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 - supported

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).

0:05:50supportedmoderateStuart 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.

0:13:48supportedhighStuart 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.

0:16:28supportedmoderateStuart 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.

0:28:10supportedhighStuart 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.

0:31:41supportedhighStuart 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.

0:49:58supportedhighStuart 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).

1:46:46supportedhighStuart 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.

Fact-checked episodes

Publications