In the Diabetes Prevention Program, a multicenter trial in patients with impaired glucose tolerance, intensive lifestyle modification aimed at a weight loss of 7 percent reduced the rate of progression from impaired glucose tolerance to diabetes by 58 percent.
Factors that predict response to a diet include dietary adherence and genetic factors influencing body composition and energy expenditure.
Approximately 22 kcal/kg is required to maintain a kilogram of body weight in a normal-weight adult. Thus, the expected or calculated energy expenditure for a woman weighing 100 kg is approximately 2200 kcal/day. The variability of ±20 percent could give energy needs as high as 2620 kcal/day or as low as 1860 kcal/day.
The goal of dietary therapy, therefore, is to reduce the total number of calories consumed. We suggest choosing a dietary pattern of healthful foods, such as the Dietary Approaches to Stop Hypertension (DASH) or Mediterranean-style diet, rather than focusing on a specific nutrient.
Diets which emphasize reductions in refined carbohydrates, processed meats, and foods high in sodium and trans fat; moderation in unprocessed red meats, poultry, eggs, and milk; and high intakes of fruits, nuts, fish, vegetables, vegetable oils, minimally processed whole grains, legumes, and yogurt are preferred.
Weight-reducing diets should eliminate alcohol, sugar-containing beverages, and most highly concentrated sweets because they may not contain adequate amounts of other nutrients besides energy.
The DASH diet is comprised of four to five servings of fruit, four to five servings of vegetables, two to three servings of low-fat dairy per day, and <25 percent dietary intake from fat. The DASH diet has been studied in both normo- and hypertensive populations and found to lower systolic and diastolic pressure more than a diet rich in fruits and vegetables alone
Low- (60 to 130 grams of carbohydrates) and very-low (0 to <60 grams) carbohydrate diets are more effective for short-term weight loss than low-fat diets, although probably not for long-term weight loss. A meta-analysis of five trials found that the difference in weight loss at six months, favoring the low-carbohydrate over low-fat diet, was not sustained at 12 months.
Restriction of carbohydrates leads to glycogen mobilization and, if carbohydrate intake is less than 50 g/day, ketosis will develop. Rapid weight loss occurs, primarily due to glycogen breakdown and fluid loss rather than fat loss. In addition, very-low-carbohydrate, ketogenic diets are associated with a small increase in energy expenditure that wanes over time [43].
During 26 years of follow-up of women in the Nurses' Health Study and 20 years of follow-up of men in the Health Professionals' Follow-up Study, low-carbohydrate diets in the highest versus lowest decile for vegetable proteins and fat were associated with lower all-cause mortality (hazard ratio [HR] 0.80, 95% CI 0.75-0.85) and cardiovascular mortality (HR 0.77, 95% CI 0.68-0.87) [45]. In contrast, low-carbohydrate diets in the highest versus lowest decile for animal protein and fat were associated with higher all-cause (HR 1.23, 95% CI 1.11-1.37) and cardiovascular (HR 1.14, 95% CI 1.01-1.29) mortality.
Complications of Low- or very low-carb diets
constipation (68 versus 35 percent), headache (60 versus 40 percent), halitosis (38 versus 8 percent), muscle cramps (35 versus 7 percent), diarrhea (23 versus 7 percent), general weakness (25 versus 8 percent), and rash (13 versus 0 percent)
Advantages of High-protein diets
Very-low-calorie diets have not been shown to be superior to conventional diets for long-term weight loss.