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


METHODS
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).


CONCLUSIONS
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.
Johnstone
Alexandra M
AM
Division of Obesity and Metabolic Health and Biomathematics and Statistics Scotland, Rowett Research Institute, Aberdeen, United Kingdom. a.johnstone@rowett.ac.uk
Horgan
Graham W
GW
Murison
Sandra D
SD
Bremner
David M
DM
Lobley
Gerald E
GE
D000328:Adult; D000368:Aged; D001066:Appetite / Q000187:drug effects / Q000502:physiology*; D001823:Body Composition / Q000187:drug effects / Q000502:physiology; D018592:Cross-Over Studies; D050528:Diet, Carbohydrate-Restricted; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006815:Hunger / Q000187:drug effects / Q000502:physiology*; D007662:Ketosis / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy*; D012307:Risk Factors; D015431:Weight Loss
D004040:Dietary Carbohydrates; D004044:Dietary Proteins