It is not known how a low-carbohydrate, high-protein, high-fat diet causes weight loss or how it affects blood glucose levels in patients with type 2 diabetes.
Dr Boden and colleagues from Philadelphia, America aimed to determine the effects of a strict low-carbohydrate diet on body weight, body water, energy intake and expenditure, glycemic control, insulin sensitivity, and lipid levels in obese patients with type 2 diabetes.
The researchers conducted an inpatient comparison of 2 diets at the general clinical research center of a university hospital over 3 weeks.
The investigators included 10 obese patients with type 2 diabetes receiving their usual diets for 7 days followed by a low-carbohydrate diet (20 grams of carbohydrates
per day, as specified in the Atkins induction diet) for 14 days.
Body weight, water, and composition; energy intake and expenditure; diet satisfaction; hemoglobin A1c; insulin sensitivity; 24-hour urinary ketone excretion; and plasma profiles of glucose, insulin, leptin, and ghrelin were measured by the research team.
The team noted that on the low-carbohydrate diet, mean energy intake decreased from 3,111 kcal/d to 2,164 kcal/d.
|On reduced carbohydrates, participants went from excessive caloric intake to normal caloric intake appropriate to their height|
|Annals of Internal Medicine|
The mean energy deficit of 1,027 kcal/d (median, 737 kcal/d) completely accounted for the weight loss of 1.7 kg in 14 days (median, 1.3 kg in 14 days).
The investigators found that on the very low-fat diet, participants spontaneously reduced their calories by about 1,000 per day, indicating that this would determine a large fat reduction as 1 gram of fat equals 9 calories.
The carbohydrates actually stimulated the patients' big appetites during the regular-diet week.
When the carbohydrates were reduced, participants went from an excessive caloric intake to a normal caloric intake that was appropriate to their height and weight.
The researchers also noted that mean 24-hour plasma profiles of glucose levels normalized, mean hemoglobin A1c decreased from 7.3% to 6.8%, and insulin sensitivity improved by approximately 75%.
In addition, the investigators found that mean plasma triglyceride decreased by 35% and cholesterol levels decreased by 10%.
The investigative team reported that the study was limited by the short duration, small number of participants, and lack of a strict control group.
Dr Boden concludes, “Weight loss, much improved 24-hour blood glucose profiles, insulin sensitivity, and hemoglobin A1c; and decreased plasma triglyceride and cholesterol levels was completely accounted for by reduced caloric intake.”
”We proved that people lose weight on the Atkins diet because they consume fewer calories, not because they get bored with the diet or lose body water or because the carbohydrate calories are treated differently by the body than fat or protein calories.”
”You don't have to cut carbs as drastically as the participants did, but if you cut carbs modestly, you cut calories, and you'll lose weight."
“The long-term effects of this diet, however, remain uncertain.”