A neat little study was published in the January 2008 American Journal of Clinical Nutrition - Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum.
In the study, researchers followed seventeen obese men, confined to a metabolic ward, for a month while they consumed either a low-carb ketogenic diet or a moderate carbohydrate diet on an ad libitum basis (eat as much as desired from foods allowed).
Over the course of the study, the protein intake of both dietary regiments was fixed to provide 30% of calories; carbohydrate was restricted to 4% of total calories in the men consuming the low-carb diet and 22% in the men consuming the moderate carbohydrate diet; and fat intake rounded out the calories in each diet with no specific limitation on fat consumption in either.
All meals were prepared and provided as requested by the men and they were allowed to eat whatever they wanted of the allowed foods in each meal with no restrictions other than on their carbohydrate options. The men on the low-carb diet consumed less calories each day on their own and reported higher feelings of satiety while on the diet.
On average, the difference in carbohydrate intake was great - the men on the low-carb diet consumed just 22g of carbohydrate each day, while those on the moderate carbohydrate diet consumed 170g each day. Both levels of intake were significant reductions from baseline, where the men averaged 396g of carbohydrate each day.
Weight loss was greater for the men following the low-carb diet, who averaged a weight loss of 6.34kg (13.95-pounds) compared to the moderate carb diet averaging a loss of 4.35kg (9.57-pounds). Calorie differences between the two groups do not fully explain the greater weight loss in the men consuming the low-carb diet since they ate about 1731-calories a day compared to the men consuming the moderate carb diet consuming about 1898-calories a day. This difference - about 167-calories a day - translates to a month long difference of 5016-calories, or 1.43-pounds....yet the difference between the two groups was 4.38-pounds greater weight loss in those on the low-carb diet.
Digging deeper into the published data we also find that the men on the low-carb diet experienced statistically significant improvements in blood glucose, insulin and HOMA-IR, as well as favorable improvements in their cholesterol levels with a reduction in total cholesterol and LDL, an increase in HDL and a significant reduction in triglycerides.
All of these favorable changes occured while the men consumed a dietary fat intake similar to that at baseline. Where at baseline they consumed an average of 126g of total fat with 43.8g of saturated fat, their dietary intake while following low-carb didn't change much - they averaged 129g of total fat on the low-carb diet and 46.3g of saturated fat. This basically highlights that modifying one's diet to be low-carb does not mean one suddenly increases dietary fat consumption significantly - in this trial, dietary fat was pretty much the same compared to baseline.
So, with this study, we have one more to add to the pile that supports carbohydrate restriction for satiety, ad libitum-spontaneous calorie reduction, weight loss, improvements to glucose, insulin and insulin resistance, along with favorable improvements (although not statistically different from the moderate carbohydrate diet) to lipids.