Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum

Alexandra M Johnstone, Graham W Horgan, Sandra D Murison, David M Bremner, Gerald E Lobley

Research output: Contribution to journalArticlepeer-review

272 Citations (Scopus)


Background: Altering the macronutrient composition of the diet influences hunger and satiety. Studies have compared high- and low-protein diets, but there are few data on carbohydrate content and ketosis on motivation to eat and ad libitum intake.

Objective: We aimed to compare the hunger, appetite, and weight-loss responses to a high-protein, low-carbohydrate [(LC) ketogenic] and those to a high-protein, medium-carbohydrate [(MC) nonketogenic] diet in obese men feeding ad libitum.

Design: Seventeen obese men were studied in a residential trial; food was provided daily. Subjects were offered 2 high-protein (30% of energy) ad libitum diets, each for a 4-wk period—an LC (4% carbohydrate) ketogenic diet and an MC (35% carbohydrate) diet—randomized in a crossover design. Body weight was measured daily, and ketosis was monitored by analysis of plasma and urine samples. Hunger was assessed by using a computerized visual analogue system.

Results: Ad libitum energy intakes were lower with the LC diet than with the MC diet [P = 0.02; SE of the difference (SED): 0.27] at 7.25 and 7.95 MJ/d, respectively. Over the 4-wk period, hunger was significantly lower (P = 0.014; SED: 1.76) and weight loss was significantly greater (P = 0.006; SED: 0.62) with the LC diet (6.34 kg) than with the MC diet (4.35 kg). The LC diet induced ketosis with mean 3-hydroxybutyrate concentrations of 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).

Conclusion: In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets.

Original languageEnglish
Pages (from-to)44-55
Number of pages12
JournalThe American Journal of Clinical Nutrition
Issue number1
Publication statusPublished - Jan 2008


  • ketogenic low-carbohydrate diets
  • weight loss
  • high-protein diets
  • body composition
  • low-fat diet
  • low-carbohydrate diets
  • body-composition
  • insulin-resistance
  • randomized-trial
  • energy-intake
  • food-intake
  • hormonal responses
  • healthy-adults
  • free mass


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