Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum.
Level 2 - randomized trial
Randomized crossover clinical trial
PubMed 18175736 · doi:10.1093/ajcn/87.1.44
What was done
Seventeen obese men participated in a residential, randomized crossover trial comparing two ad libitum, high-protein (30% of energy) diets for 4 weeks each: a low-carbohydrate ketogenic diet (LC; 4% carbohydrate) and a medium-carbohydrate nonketogenic diet (MC; 35% carbohydrate). All food was provided daily. Outcomes included daily body weight, plasma and urinary 3-hydroxybutyrate concentrations, hunger assessed by a computerized visual analogue system, and ad libitum energy intake.
What was found
Ad libitum energy intake was significantly lower on the LC diet compared to the MC diet (7.25 vs. 7.95 MJ/day; P = 0.02; standard error of the difference [SED]: 0.27). Hunger ratings were significantly lower on the LC diet (P = 0.014; SED: 1.76). Over the 4-week period, weight loss was greater on the LC diet than the MC diet (6.34 kg vs. 4.35 kg; P = 0.006; SED: 0.62). The LC diet induced ketosis, with mean 3-hydroxybutyrate concentrations reaching 1.52 mmol/L in plasma (P = 0.036 from baseline; SED: 0.62) and 2.99 mmol/L in urine (P < 0.001 from baseline; SED: 0.36).
Why it matters
This study shows that holding dietary protein constant, restricting carbohydrates sufficiently to induce ketosis provides an additional short-term suppression of hunger and spontaneous energy intake in obese men.
Limits
The trial had a small sample size (n = 17) and enrolled only obese men, limiting generalizability to women and non-obese individuals. The intervention duration was short (4 weeks per arm) in a highly controlled residential setting, leaving long-term adherence, appetite effects, and body composition changes (such as lean mass versus water loss) unmeasured in the abstract.
Cited by
- supports Starting a ketogenic diet lowers blood glucose and insulin levels, causing an immediate loss of water weight followed by an automatic reduction in caloric intake.