HoldsUp

Stuart Phillips

McMaster University

Stuart Phillips, PhD, is a professor of kinesiology and the director of the Physical Activity Centre of Excellence at McMaster University. His research focuses on the roles of exercise and nutrition in regulating human skeletal muscle protein turnover and body composition, particularly during aging. His published work investigates resistance training protocols, muscle hypertrophy mechanisms, dietary protein requirements, and physical function recovery.

47 claims checked on air: 1 context 1 contradicted 27 supported 18 unverified 1 flagged

What they said on air

0:02:07needs contexthighStuart Phillips, PhD, on Building Muscle with Resistance Exe

The human body is approximately 70% water by content, with most of that water contained within cells and skeletal muscle mass.

"So I think most people will probably understand we're about almost 70% by content water, and most of that water is inside our cells, and a lot of is inside muscle mass." (said at 0:02:07)

Total body water in healthy adults typically ranges from 50% to 60% of total body weight (averaging approximately 60% in adult males and 50–55% in adult females, though fat-free/lean mass itself is approximately 73% water). The claim is accurate that the majority of body water resides intracellularly (intracellular water comprises roughly two-thirds or ~60–65% of total body water) and that skeletal muscle tissue represents the largest reservoir of this fluid.

0:02:18supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Lean muscle mass is highly hydrated tissue, whereas fat mass contains very little water.

"So what we call muscle mass or lean mass is very hydrated tissue. Fat mass is actually not." (said at 0:02:18)

Body composition literature confirms that fat-free (lean) mass is a highly hydrated tissue compartment, with total water content consistently measured at approximately 70% to 73% across children, young adults, older adults, and athletes. In contrast, lipid/fat mass contains negligible water (and whole adipose tissue consists primarily of triglycerides with comparatively little water).

0:05:43unverifiedlowStuart Phillips, PhD, on Building Muscle with Resistance Exe

On a population level, aging humans lose approximately 1% of muscle mass per year.

"And usually what we say on a population level, it's about a 1% loss of muscle mass per year" (said at 0:05:43)

No published record matching the claim that aging humans lose approximately 1% of muscle mass per year on a population level was located in the evaluated abstracts; this does not prove the claim false. While progressive age-related loss of skeletal muscle mass and function (sarcopenia) is well-documented in clinical consensus literature, specific population-wide rate estimates vary depending on the age cohort, sex, measurement modality, and physical activity levels.

0:05:50supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

On a population level, humans lose muscle strength and power at a rate of approximately 1% to 3% per year, which is faster than the rate of muscle mass loss.

"and about a 1 to 3% drop in strength or power. So the muscle mass decline is actually slower than we lose strength" (said at 0:05:50)

Longitudinal cohort studies and systematic reviews demonstrate that muscle strength and power decline significantly faster with age than muscle mass. Large longitudinal studies (such as the Health ABC Study) indicate that older adults lose muscle strength at approximately 2% to 4% per year, which is roughly 2 to 5 times faster than the rate of muscle mass loss (which typically declines at around 0.5% to 1% per year).

0:06:52supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Both men and women can build bone mass up until approximately age 30.

"women in particular are told that we can we can build bone mass up until probably about 30. Men, it's about the same." (said at 0:06:52)

Published longitudinal cohort studies and endocrine consensus establish that peak bone mass (the maximum bone mineral accrual) is reached during the third decade of life (between the mid-20s and approximately age 30) in both males and females. Although the majority of bone mass is accrued during adolescence, consolidation and accumulation of bone mineral density and content continue into young adulthood until peak bone mass is achieved around this age window.

0:07:50supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Studies in nonagenarians show that lifting weights can increase muscle strength and restore functional ability.

"But there are even studies in nonagenarians, you know, people in their 90s, lifting weights and they can get stronger. They're now gaining muscle not so much, but they get function back." (said at 0:07:50)

A landmark study by Fiatarone et al. (1990) evaluated 8 weeks of high-intensity resistance training in frail, institutionalized individuals aged 90 ± 1 years (up to 96 years old). The participants achieved substantial improvements in muscle strength (an average increase of 174%), modest increases in muscle cross-sectional area (9.0%), and notable gains in functional mobility, including a 48% improvement in tandem gait speed.

0:10:18supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Population data show that meeting guidelines of 150 minutes of moderate-to-vigorous physical activity and two days of muscle-strengthening exercises per week is associated with an average of approximately four extra years of life.

"once you hit that sort of 150 minutes of moderate to vigorous, whichever, okay, that's the guidelines, and I think you maintain your strength and so make sure you do those two days of strengthening exercises a week. We get obviously we get on average, when you look at population data, about four extra years of life." (said at 0:10:18)

Large-scale pooled population studies support the claim that meeting standard physical activity guidelines is associated with approximately 3 to 4.5 additional years of life expectancy compared to inactivity. In a pooled analysis of six prospective cohort studies including 654,827 individuals (Moore et al., 2012), meeting the minimum recommended level of physical activity (equivalent to 150 minutes of brisk walking per week, or 7.5 to <15 MET-hours/week) was associated with a 3.4-year gain in life expectancy after age 40, increasing up to 4.5 years with higher activity levels. Similarly, prospective analyses in the UK Biobank (Chudasama et al., 2019) have shown that achieving recommended physical activity levels adds approximately 3.1 to 5.3 life years depending on baseline health status and activity measure.

0:10:19unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Androgen deprivation therapy in men with prostate cancer induces a hypogonadal state accompanied by muscle mass loss.

"if you take men and they have a diagnosis of prostate cancer, they're often put on androgen deprivation therapy. So they're taken from a normal testosterone state to a hypogonadal state, and yeah, they lose muscle mass." (said at 0:10:19)

The claim is well supported. Androgen deprivation therapy (ADT) for prostate cancer suppresses circulating testosterone to castrate (hypogonadal) levels. A well-established adverse effect of this severe testosterone suppression is a significant decline in skeletal muscle and lean body mass, which often leads to sarcopenia and increases in fat mass unless counteracted with targeted resistance exercise. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

0:13:48supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Different animal classes excrete excess nitrogenous waste from protein metabolism in distinct forms: fish excrete ammonia, birds excrete uric acid, and mammals excrete urea.

"Every species has evolved a way of getting rid of extra protein: fish, it's ammonia; birds, it's uric acid; mammals, it's urea." (said at 0:13:48)

Comparative animal physiology establishes that aquatic animals (such as fish) primarily excrete nitrogenous waste as ammonia (ammonotely), terrestrial mammals convert nitrogen waste to urea (ureotely), and birds and reptiles convert it to uric acid (uricotely) (PMID: 7699310, PMID: 12042332). While environmental shifts or dietary conditions can alter secondary excretion pathways in specific species (such as nectarivorous birds under high water throughput, PMID: 12042332), the general rule for primary nitrogenous waste excretion across these major animal groups matches the speaker's statement.

0:15:48contradictedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Nitrogen balance studies used to establish the RDA for protein are prone to errors due to incomplete collection and overestimation of nitrogen losses.

"The original studies that led to the derivation of the Recommended Dietary Allowance are what we call nitrogen balance... Those studies we've known for a long time are problematic because of incomplete collection, overestimation, etc., of losses." (said at 0:15:48)

While dietary reference values (such as the Recommended Dietary Allowance) for protein were historically established using nitrogen balance studies, the speaker states the direction of the methodological error backwards. In classical nitrogen balance studies, incomplete collection of urine/feces and unmeasured miscellaneous routes (such as sweat, hair, skin desquamation, and flatus) lead to an underestimation of nitrogen losses (output) and an overestimation of intake, resulting in an artificially positive balance and potential underestimation of true protein requirements, rather than an overestimation of losses.

0:16:28supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Alternative protein requirement assessment methods using stable isotopes indicate that human protein requirements to maintain balance are closer to 1.2 grams per kilogram of body weight per day.

"there are alternative approaches using stable isotopes that have consistently shown that people actually need—when I say need, to maintain the balance that we talk about—higher intakes. And so that's the 1.2." (said at 0:16:28)

Studies using stable isotope tracer methods, specifically the indicator amino acid oxidation (IAAO) technique (such as with L-[1-¹³C]phenylalanine), consistently indicate that the population-safe protein requirement (comparable to the Recommended Dietary Allowance) for adult humans is approximately 1.2 g/kg/day, with an estimated average requirement of ~0.93 g/kg/day. This is roughly 40–50% higher than traditional recommendations of 0.8 g/kg/day derived from historical nitrogen balance studies.

0:20:05supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Head-to-head primate studies investigating caloric restriction and lifespan extension have yielded conflicting results, with caloric restriction failing to extend lifespan in one of the two major study sites.

"when we compare primates head-to-head, so this is in caloric restriction, arguably the most robust model of survival extending lifespan, the data is actually conflicting. It's only been done, obviously, in two different locations, and so if you were a primate, you know, in one location, you did better than primates in the other, but the net result was it actually didn't extend lifespan." (said at 0:20:05)

The claim is supported. Only two major longitudinal studies have evaluated the effects of lifelong caloric restriction (CR) on lifespan in nonhuman primates (rhesus macaques). In 2009 and 2014, the University of Wisconsin (WNPRC) study reported that CR significantly extended survival and reduced mortality, whereas the 2012 report from the National Institute on Aging (NIA) study found that CR did not extend overall survival. Later collaborative analyses identified that differences in study protocols, baseline diet composition, and age of onset accounted for these conflicting findings.

0:24:10supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Spending six months to a year in space results in the equivalent of 10 to 15 years of skeletal and muscle aging.

"And we know that, you know, six months or a year spending up at the space station is about 10 to 15 years of skeletal and muscle aging, and it's tough to get back." (said at 0:24:10)

The claim is supported. Long-duration spaceflight (4 to 12 months) induces accelerated bone and muscle loss that mimics multiple years to decades of natural terrestrial aging. In a study evaluating astronauts after 4 to 6 months on the International Space Station, proximal femoral bone strength and mineral density decreased at rates of approximately 1% to 2.6% per month in weight-bearing bones, resulting in cumulative losses equivalent to 10 to 15 or more years of age-related bone decline on Earth. Furthermore, studies tracking astronauts post-flight demonstrate that structural bone loss and trabecular microarchitectural deficits can persist for years and are difficult to completely recover.

0:25:47unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Exercise training can increase the size of the hippocampus in the human brain.

"15, 20 years ago if you said, "Well, you can change the size of your hippocampus and your brain with exercise," they'd have been like, "Right."" (said at 0:25:47)

Randomized controlled trials and meta-analyses demonstrate that exercise training can modify hippocampal volume in humans. In a landmark randomized controlled trial of 120 older adults, 1 year of aerobic exercise training increased anterior hippocampal volume by approximately 2%, reversing age-related volume loss. Subsequent systematic reviews and meta-analyses of controlled exercise trials have confirmed significant positive effects on hippocampal volume compared to non-exercising controls, primarily reflecting a combination of volume enlargement and preservation against expected age-related atrophy. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

0:25:55unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Exercise produces improvements in depressive and anxiety symptoms of a magnitude comparable to pharmaceutical interventions.

"You get, you know, improvements in mood, you get improvements in depressive symptoms, anxiety, and everything, almost of the magnitude similar to people taking pharmaceutical interventions for those things." (said at 0:25:55)

Systematic reviews and network meta-analyses of randomized controlled trials demonstrate that exercise and physical activity produce reductions in depressive and anxiety symptoms with effect sizes comparable to antidepressant medications and standard psychological interventions, particularly in non-severe depression. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

0:28:10supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Beyond approximately 1.6 grams of protein per kilogram of body weight per day, additional protein intake does not further support muscle protein synthesis or lean mass accrual.

"I think 1.6 grams per kilo—and I know people like to talk in pounds, so you know, it's something around sort of 0.6 to 0.7 grams per pound—and those levels, after that, you can digest and eat lots more protein, your body just can't use it." (said at 0:28:10)

A systematic review and meta-analysis of 49 randomized controlled trials involving 1,863 participants undergoing resistance exercise training found that dietary protein intake significantly augmented gains in fat-free mass and muscle strength up to a plateau of 1.62 g/kg/day (95% CI: 1.03 to 2.20 g/kg/day). Beyond approximately 1.6 g/kg/day, higher protein intakes did not further increase resistance training-induced gains in lean body mass.

0:28:50unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Heat shock proteins act as molecular chaperones that prevent protein misfolding and help mitigate muscle atrophy.

"what we understand now is that they chaperone, or they act as essentially little proteins that bind to other proteins to prevent them from being what we call misfolded... And we're beginning to see more and more that you can alleviate muscle atrophy" (said at 0:28:50)

Heat shock proteins (HSPs) are a well-characterized family of molecular chaperones whose primary function is assisting proper protein folding and preventing the aggregation of misfolded or damaged proteins. Extensive preclinical and mechanistic research demonstrates that HSPs (such as Hsp70, Hsp90, Hsp25, and αB-crystallin) protect skeletal muscle proteostasis, suppress key atrogenic pathways (including the ubiquitin-proteasome and autophagy-lysosome systems), and help mitigate muscle wasting during conditions of disuse, denervation, and aging. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

0:31:41supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

For younger individuals performing resistance training, consuming 1.6 grams of protein per kilogram of body weight per day optimizes lean body mass gains.

"if you're younger and you're resistance training, so you're lifting weights, you want to get a bit bigger, a bit stronger, 1.6 grams of protein per kilo per day was the, the type of intake that you need to consume." (said at 0:31:41)

A landmark systematic review and meta-analysis of 49 randomized controlled trials encompassing 1,863 participants performing resistance exercise training evaluated the effect of total protein intake on gains in fat-free mass and strength. Using breakpoint regression analysis, the authors demonstrated that gains in fat-free mass plateaued at a total daily protein intake of approximately 1.62 g/kg/day (95% CI: 1.03–2.20 g/kg/day), with no further benefits observed at higher intakes. The analysis also found that the efficacy of protein supplementation on fat-free mass gains was greater in younger adults compared to older adults.

0:33:43supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Caloric deficits act as a catabolic stimulus on skeletal muscle.

"Again, you're sort of tipping the scales in the favor of the breakdown side of things. That's just, you know, calorie deficits are catabolic stimuli, and it's catabolic for muscle too." (said at 0:33:43)

Caloric deficits induce a catabolic environment in skeletal muscle, shifting net muscle protein balance into a negative state. Human randomized trials show that dietary energy restriction reduces muscle protein synthesis (MPS) without necessarily altering muscle protein breakdown (MPB), which leads to net muscle protein loss unless mitigated by sufficient protein intake and resistance training.

0:39:18supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Muscle protein is made up of 20 amino acids, of which 9 are essential and 3 are branched-chain amino acids.

"if that's muscle protein, it's made up of 20 different types of bricks. Those are the 20 amino acids that we have, nine of which are essential, we need to get them in our diet. And in particular, they're a group of what are called branched-chain amino acids that are three of the nine" (said at 0:39:18)

Standard human biochemistry establishes that body proteins, including muscle proteins, are composed of 20 standard proteinogenic amino acids. Of these, 9 are nutritionally essential (cannot be synthesized de novo in sufficient quantities by humans and must be obtained from the diet), and 3 of these 9 essential amino acids are branched-chain amino acids (leucine, isoleucine, and valine).

0:39:40supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Leucine triggers muscle protein synthesis in a dose-dependent manner up to a plateau point.

"the most potent, if you like, of the three branched chains is an amino acid called leucine. And the way I like to explain it to people is that it's kind of like the the brick that when it arrives, it turns the process on... So once you have sufficient leucine there, you can turn the switch up as bright as it can go. Once you put more leucine there, you can't go any higher." (said at 0:39:40)

The speaker accurately describes the 'leucine trigger' and 'leucine threshold' models of muscle protein synthesis (MPS). Leucine acts as a primary signaling molecule activating the mammalian target of rapamycin complex 1 (mTORC1) pathway. In acute nutritional studies, stimulating MPS exhibits a dose-dependent response to leucine up to a saturating threshold (typically ~2 to 3 g per dose), beyond which additional leucine yields no further acute increase in synthesis rates. Systematic reviews confirm this trigger/threshold dynamic for isolated protein ingestion and acute postprandial MPS regulation, particularly in older adults, although long-term phenotypic adaptations also depend heavily on total daily protein intake.

0:40:29supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Aging reduces sensitivity to leucine, requiring higher amounts of leucine, branched-chain amino acids, or essential amino acids to stimulate muscle protein synthesis.

"For older people, for reasons that we're beginning to unravel now, I think what happens is now the sensitivity of that dimmer switch—so the leucine comes and you sort of get this response, and a younger person, you might get that. And so we need more leucine or more branched chains or more essential amino acids, which translates into more—you need more protein to trigger the whole turning the protein synthetic process on." (said at 0:40:29)

The speaker's statement accurately reflects clinical and metabolic trial evidence regarding age-related anabolic resistance. Controlled metabolic studies utilizing stable isotope tracers and muscle biopsies demonstrate that older adults exhibit an attenuated muscle protein synthesis (MPS) response to standard doses or proportions of essential amino acids/leucine compared to younger adults, and that higher doses of leucine or overall protein are necessary to overcome this threshold and stimulate MPS.

0:41:40supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Plant-derived proteins contain anti-nutritional factors like fiber and phytates that can inhibit protein breakdown enzymes and reduce amino acid bioavailability.

"Plant-derived proteins have anti-nutritional—fiber is one, phytates, lots of other things that can inhibit protein breakdown enzymes. And you know, you say that's a big deal, it's going to lower the quality, you're not going to get as many amino, essential amino acids." (said at 0:41:40)

Plant-derived protein sources naturally contain antinutritional factors (ANFs)—including protease/trypsin inhibitors, phytates (phytic acid), tannins, and insoluble dietary fiber—that can inhibit digestive enzymes, complex with proteins, and reduce protein digestibility and essential amino acid bioavailability compared to animal protein sources. Conventional and novel food processing techniques (e.g., cooking, soaking, fermentation, and extraction) are widely used specifically to reduce or deactivate these factors.

0:42:53supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Preparation methods such as cooking, sprouting, and fermentation liberate plant proteins and reduce anti-nutritional effects, increasing bioavailability.

"a lot of the prep methods of plant proteins like beans and legumes, you cook them, and cooking actually liberates a lot of the proteins that makes them more bioavailable and so reduces the anti-nutritional effects. So sprouting, cooking, fermentation, all kinds of things that are commonly done with plant-based proteins, beans, legumes, I think are making the two proteins much more close in quality inside us than we once thought." (said at 0:42:53)

Extensive food science and nutritional literature confirms that traditional preparation and processing methods—including thermal cooking, germination (sprouting), and fermentation—degrade or inactivate antinutritional factors (such as trypsin inhibitors, lectins, phytic acid, and tannins) and alter protein structure, thereby enhancing protein digestibility and nutrient bioavailability in legumes and pulses.

0:47:25supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Branched-chain amino acid (BCAA) supplements provide minimal additional benefit for muscle protein synthesis beyond the specific action of leucine.

"I think the message is fairly clear now that they're largely—I won't say useless, but from useful to useless, they're a lot closer to the useless end. But it's only the leucine out of those three amino acids that's the important branched-chain amino acid, so they work because of the leucine." (said at 0:47:25)

The speaker's assertion is supported by metabolic and clinical evidence. Leucine is the specific branched-chain amino acid that acts as a key trigger for muscle protein synthesis (MPS) signaling via the mTORC1 pathway. However, isolated BCAA supplements (which supply only leucine, isoleucine, and valine without the full complement of all nine essential amino acids) cannot sustain elevated protein synthesis because all essential amino acids are required as substrates. Consequently, isolated BCAA supplements provide negligible practical benefit for building muscle compared to whole dietary protein sources or complete essential amino acid mixtures.

0:48:57unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Free-form leucine is readily absorbed by the body.

"No, you absorb it in free form. In fact, it's really readily absorbed." (said at 0:48:57)

No published record matching the claim that free-form leucine is readily absorbed by the body was located; this does not prove the claim false.

0:49:58supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Adding supplemental leucine to a suboptimal or low-protein dose stimulates muscle protein synthesis to a level comparable to a higher-protein dose.

"if you take even a small protein dose and you add a little bit of extra leucine, you can make it look as if it's a bigger protein dose." (said at 0:49:58)

Randomized trials demonstrate that supplementing a suboptimal, low dose of protein (e.g., 6.25 g of whey protein) with additional leucine stimulates acute rates of myofibrillar protein synthesis (MPS) to levels comparable to a standard higher-protein dose (e.g., 25 g of whey protein). For example, Churchward-Venne et al. (2014) showed that 6.25 g of whey supplemented to 5.0 g of total leucine stimulated 0–4.5 h postprandial MPS equivalently to 25 g of whey protein in healthy young men.

0:50:25supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

The optimal per-meal leucine dose to stimulate muscle protein synthesis is approximately 3 to 4 grams for older adults and 2 to 3 grams for younger adults.

"the per-meal leucine dose is probably somewhere in the range of sort of three to four grams for an older person, probably two to three for younger, and that's just because the younger person is really sensitive to the effects." (said at 0:50:25)

The claim accurately summarizes the established 'leucine trigger' concept in protein metabolism. Younger adults are more sensitive to amino acid stimulation and generally saturate muscle protein synthesis (MPS) with approximately 2 to 3 g of leucine per meal (roughly 20–25 g of high-quality protein). In contrast, older adults exhibit age-related anabolic resistance and require a higher leucine threshold of roughly 3 to 4 g per meal (roughly 35–40 g of protein) to achieve a robust postprandial MPS response.

0:50:40supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Local limb immobilization in younger adults induces muscle atrophy and creates an anabolic resistance response similar to that seen in older adults.

"But we can make a younger person, when we put a brace on their leg and we get local atrophy, their—atrophied muscle looks like an older person's response. So the disuse response, we think, is sort of—it's almost a model of premature aging in terms of your muscle, anyway." (said at 0:50:40)

The speaker's claim is supported. Experimental models of limb immobilization and physical disuse in healthy young adults induce rapid skeletal muscle atrophy, declines in muscle protein synthesis, and anabolic resistance to nutritional and exercise stimuli. In muscle physiology research, disuse paradigms (such as knee bracing, casts, or step reduction) are widely recognized and utilized as human models for studying the phenotypic and metabolic characteristics of premature aging and sarcopenia.

0:51:15supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Abrupt step reduction induces anabolic resistance in older individuals.

"We have done some studies where we've used step reduction, like abrupt step reduction, as a model of sort of abrupt sedentarism, where we can make older people much more anabolically resistant as a result of that." (said at 0:51:15)

Human metabolic studies demonstrate that short-term, abrupt step reduction (such as reducing daily steps by ~75–80% for 14 days) induces anabolic resistance in older adults, characterized by a significant blunting of postprandial myofibrillar protein synthesis and accelerated loss of leg fat-free mass.

0:51:58supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Aging impairs insulin-mediated capillary recruitment and vasodilation in skeletal muscle without necessarily causing overt glycemic insulin resistance.

"when you turn on insulin, you usually open up blood vessels to allow flow to happen. And what we think happens with aging is that response becomes just a little bit less sensitive. You're not insulin resistant from the perspective of blood sugar, but from a protein perspective, we think that opening up local capillaries and allowing good blood flow in older people just isn't quite as sensitive." (said at 0:51:58)

Human physiological studies demonstrate that aging is associated with impaired insulin-mediated muscle capillary recruitment and microvascular vasodilation. In healthy, non-diabetic older adults, feeding- or insulin-induced microvascular perfusion is blunted despite intact or near-normal glycemic regulation, which impairs postprandial amino acid delivery and contributes to muscle anabolic resistance. Restoring microvascular perfusion pharmacologically has been shown to rescue insulin-stimulated muscle protein synthesis in older adults.

0:53:30supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Global physical activity guidelines commonly recommend performing muscle-strengthening activities at least two days per week.

"Most of the guidelines you look around the world, there's a recommendation for two times a week of strengthening activities." (said at 0:53:30)

Major international and national physical activity guidelines, including those published by the World Health Organization (WHO) and the U.S. Department of Health and Human Services, explicitly recommend that adults perform muscle-strengthening activities involving all major muscle groups on at least 2 days per week, in addition to aerobic exercise.

0:56:33supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Resistance exercise increases the rate of muscle protein breakdown as well as muscle protein synthesis.

"And when you're lifting or you're doing any type of resistance and/or strength training, you are also causing muscle protein breakdown. GUEST1: Yeah, absolutely, yeah... physical exercise—and particularly some forms, but weightlifting is a really potent one—turns up the rate at which we're pulling bricks out of the wall. You're creating damage, you're creating a stress on the muscle. Successful adaptation to stress is that you're able to repair that damage and replace those damaged proteins, and that's the synthesis side of things." (said at 0:56:33)

Human metabolic tracer studies consistently show that resistance exercise stimulates overall muscle protein turnover by simultaneously increasing both muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In the fasted state following resistance exercise, both synthesis and degradation rates are elevated, leaving net muscle protein balance negative until exogenous amino acids/dietary protein are consumed to exceed the breakdown rate and yield net accretion.

1:01:38supportedmoderateStuart Phillips, PhD, on Building Muscle with Resistance Exe

Post-exercise restorative and recovery processes in adults are driven primarily by macronutrients, and endogenous IGF-1 does not serve as a stimulatory or inhibitory driver of muscle repair.

"Most of the rest, the restorative process and the recovery process, is driven almost exclusively by macronutrients. And so IGF-1, I'm like, yeah, it needs to be there, but it's not a stimulatory or an inhibitory hormone for repair or recovery." (said at 1:01:38)

Human experimental studies demonstrate that transient post-exercise elevations in systemic endogenous insulin-like growth factor 1 (IGF-1) do not drive or enhance post-exercise muscle protein synthesis (MPS) or muscle hypertrophy. Instead, post-exercise restorative and anabolic processes are primarily driven by local intramuscular signaling mechanosensing and macronutrient availability (such as dietary protein and amino acid ingestion).

1:03:10unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Leucine activates muscle protein synthesis primarily through mTOR signaling.

"Leucine goes through mTOR. Its dysregulation is involved in all kinds of processes, including cancer and lots of other things. So it has a really centrally important role in integrating all of those anabolic signals." (said at 1:03:10)

Extensive mechanistic and human clinical evidence demonstrates that leucine stimulates skeletal muscle protein synthesis primarily via activation of the mechanistic target of rapamycin (mTOR / mTORC1) signaling pathway. Leucine acts as a key nutrient sensor and signaling trigger for translation initiation and protein synthesis, and mTOR is widely recognized as a central integrator of anabolic signals whose dysregulation is implicated in metabolic dysfunction and oncogenesis. [citation dropped: PMID did not verify]

The search did find related studies, but none that directly tests this claim:

1:10:50unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

A meta-analysis by Brandon Roberts showed that men and women achieve the same relative muscle growth gains relative to baseline in response to resistance training.

"and this is a meta-analysis now, a guy named Brandon Roberts did this one, and you resistance train them relative to what they started with, everybody goes up the same amount. Women get the same amount of muscle growth as men do, but they had less muscle to start with" (said at 1:10:50)

A 2020 systematic review and meta-analysis led by Brandon M. Roberts evaluated sex differences in response to resistance training among young to middle-aged adults. Analyzing 12 hypertrophy outcomes across 10 studies, the authors found no statistically significant difference in relative muscle growth between males and females (effect size = 0.07 ± 0.06; p = 0.31; I² = 0%), supporting the claim that relative muscle hypertrophy gains are similar between sexes. [citation dropped: PMID did not verify]

1:16:40unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Bone composition is approximately 40% protein by weight, structured as a layer of collagenous protein.

"Your bone is actually about 40% by composition protein. It's not just a stick of chalk. There's a layer of collagenous protein around it." (said at 1:16:40)

No published record matching the specific claim that bone is approximately 40% protein by weight structured as an outer layer of collagenous protein was located; this does not prove the claim false.

1:18:45unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Individuals with Laron syndrome (growth hormone receptor deficiency) do not develop cancer.

"and this is where you've had Dr. Longo on the show before, he shows in certain populations of dwarves, for example, who have a particular type of dwarfism and lack of growth hormone receptor, they're actually—they don't get cancer." (said at 1:18:45)

Longitudinal cohort studies by Dr. Valter Longo, Dr. Jaime Guevara-Aguirre, and colleagues demonstrated that individuals with growth hormone receptor deficiency (Laron syndrome) have a dramatically reduced incidence of cancer compared to unaffected relatives, but cancer is not completely absent. In a 22-year follow-up study of the Ecuadorian cohort, one nonlethal malignancy was documented among GHR-deficient individuals (compared to a 17% cancer prevalence in unaffected controls). An international survey of 230 patients with Laron syndrome similarly observed zero reported cancer cases, indicating near-complete protection, though an absolute claim that they 'do not get cancer' slightly overstates the findings. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:25:05unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Higher levels of leisure-time physical activity are associated with a reduced risk in 13 of the 26 most common types of cancer.

"13 of the 26 most common types of cancer are lower in people who have higher levels of leisure-time physical activity." (said at 1:25:05)

A landmark pooled analysis of 12 prospective cohorts comprising 1.44 million adults (Moore et al., 2016) investigated the association between leisure-time physical activity and 26 types of cancer. Comparing high versus low levels of leisure-time physical activity (90th vs. 10th percentile), physical activity was statistically significantly associated with a reduced risk of 13 specific cancers: esophageal adenocarcinoma, liver, lung, kidney, gastric cardia, endometrial, myeloid leukemia, myeloma, colon, head and neck, rectal, bladder, and breast cancer. [citation dropped: PMID did not verify]

1:27:45unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

In adults, exogenous growth hormone acts primarily as a fat-mobilizing hormone and does not significantly promote muscle mass accretion.

"in the case of growth hormone, it's actually a fat-mobilizing hormone. That's one of its great side effects if you're taking exogenous growth hormone; you notice you get leaner. It probably doesn't do much for your muscle." (said at 1:27:45)

Multiple systematic reviews and meta-analyses of randomized controlled trials confirm that exogenous growth hormone (GH) acts primarily as a potent lipolytic (fat-mobilizing) agent, reducing body fat mass and increasing circulating free fatty acids and glycerol. Although GH administration increases measured lean body mass (or fat-free mass), studies demonstrate that this change is driven primarily by extracellular fluid retention and connective tissue synthesis rather than myofibrillar muscle protein synthesis, contractile muscle hypertrophy, or gains in muscle strength. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:35:28unverifiedlowStuart Phillips, PhD, on Building Muscle with Resistance Exe

The heat shock protein response can be locally induced by heating a single limb rather than requiring whole-body hyperthermia.

"it seems that the heat shock response is something you can locally induce, right? It doesn't have to be a sauna, so you can heat one leg and not the other leg, for an example." (said at 1:35:28)

No published record matching the claim that the heat shock response can be locally induced by heating a single limb rather than requiring whole-body hyperthermia was located; this does not prove the claim false.

1:35:48unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Local tissue heating opens capillaries and increases tissue perfusion.

"And again, the cardiovascular effects to do with that and opening up capillaries and so more perfusion of them, I mean, there's all kinds of things that are suggestive that there could be something going on there, yeah, for sure." (said at 1:35:48)

Local tissue heating directly induces thermal hyperemia, increasing tissue perfusion and causing microvascular capillary recruitment (opening of capillaries). Human physiological studies show that local hyperthermia produces substantial, localized increases in microvascular blood flow and tissue oxygenation, while direct microvascular imaging confirms that heating increases the number of open, perfused capillaries and the time precapillary sphincters remain open. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:38:32unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

High-dose omega-3 supplementation attenuated disuse muscle atrophy and accelerated muscle recovery following two weeks of single-leg immobilization in young women.

"We supplemented one group with very high-dose omega-3 fatty acids and we supplemented the other group with sort of a corn oil placebo, and then we braced one of their legs for our local disuse atrophy model for two weeks. And the women on the omega-3 supplement saw a really mild disuse atrophy response, and then returned to normal much quicker than the other group who saw a much greater atrophic response and didn't get back to normal after two weeks of we call it passive remobilization." (said at 1:38:32)

The speaker accurately describes the results of a randomized controlled trial (McGlory et al., 2019) in 20 healthy young women. Participants received either 5 g/day of omega-3 fatty acids or a control oil starting 4 weeks prior to 2 weeks of unilateral leg immobilization, followed by 2 weeks of recovery. The omega-3 group showed significantly attenuated loss of muscle volume during immobilization (8% reduction vs. 14% in the control group) and fully recovered their muscle volume after 2 weeks of returning to normal activity, whereas the control group remained significantly below baseline. [citation dropped: PMID did not verify]

1:44:10unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Creatine monohydrate supplementation improves cognitive performance and brain function.

"Now the brain and the cognitive side of things is is, you know, the evidence is growing in that area, too." (said at 1:44:10)

The speaker's statement that evidence is growing regarding creatine's effects on brain and cognitive function is supported by recent systematic reviews and meta-analyses. A 2024 systematic review and meta-analysis of 16 randomized controlled trials (RCTs) found that creatine monohydrate supplementation produced modest, statistically significant improvements in memory (SMD = 0.31), attention time, and processing speed, though overall cognitive function and executive function showed no significant differences. A 2023 meta-analysis of RCTs in healthy individuals similarly demonstrated a significant positive effect of creatine supplementation on memory performance (SMD = 0.29), with pronounced benefits observed in older adults. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:44:10unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Over 40 years of research on creatine supplementation has shown no causal link to kidney damage or increased cancer incidence, with adverse events being rare.

"There was a lot of talk about it's damaging your kidneys, it's doing, you know, this you shouldn't, you know, it's a it's a guanidino compound, etc., etc. Um, we've got 40 years' worth of data with people on the supplement now and and we're not seeing some sort of rife wave of of people who used it getting various forms of cancer, etc., etc. All the data reviewing it from a safety standpoint has given it two thumbs up. The adverse events are are rare" (said at 1:44:10)

Extensive clinical trial data and multiple systematic reviews and meta-analyses show that creatine monohydrate supplementation does not cause kidney damage in healthy individuals, does not increase cancer incidence, and is generally safe with rare adverse events. While creatine intake leads to minor increases in circulating serum creatinine, true measures of renal function and glomerular filtration rate (such as Cr-EDTA clearance, serum urea, and proteinuria) remain unaffected, reflecting increased metabolic turnover of creatine rather than renal injury. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify] [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:45:46unverifiedvery lowStuart Phillips, PhD, on Building Muscle with Resistance Exe

Dr. Mark Tarnopolsky prescribes 4 to 5 grams of creatine monohydrate daily to patients with neuromuscular diseases, such as mitochondrial myopathies and muscular dystrophies, to treat muscle weakness.

"A good friend of mine, Mark Tarnopolsky, neuromuscular physician, has all of his neuromuscular patients on it. So I think that that's a fairly robust endorsement of what it can do for people with compromised muscle function, and he recommends that these people just start with a dose of about, you know, four to five grams of creatine a day." (said at 1:45:46)

Dr. Mark Tarnopolsky, a neuromuscular specialist and researcher, has extensively evaluated and recommended creatine monohydrate supplementation (typically at maintenance doses of approximately 3 to 5 grams daily, or ~0.1 g/kg/day) for patients with neuromuscular and neurometabolic conditions, including muscular dystrophies and mitochondrial cytopathies. Clinical trials led by Tarnopolsky and Cochrane systematic reviews co-authored by him demonstrate that creatine monohydrate supplementation improves muscle strength and high-intensity performance in muscular dystrophies and mitochondrial cytopathies. [citation dropped: PMID did not verify] [citation dropped: PMID did not verify] [citation dropped: PMID did not verify]

1:46:46supportedhighStuart Phillips, PhD, on Building Muscle with Resistance Exe

Creatine monohydrate is the most extensively studied chemical form of creatine supplement.

"The monohydrate form is the one to to aim for. Don't be fooled by creatine insert your favorite derivative. Um, monohydrate is is the one that's been most studied, and and so probably the one you want to go for, for sure." (said at 1:46:46)

Creatine monohydrate is universally recognized in systematic reviews and scientific literature as the most extensively researched and validated form of creatine supplementation. Reviews comparing creatine monohydrate to alternative chemical formulations (such as creatine ethyl ester, magnesium-creatine chelate, creatine nitrate, pyruvate, or citrate) show that the vast majority of efficacy and safety data in humans are based on creatine monohydrate. Furthermore, alternative derivative forms have not demonstrated superior bioavailability, efficacy, or safety over monohydrate.

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