weight loss
Recent Study Shows Low Carb Diets More Effective Than Low Fat Diets Long Term
A recent study in the New England Journal of Medicine showed better fat loss over the long run with low-carb and “Mediterranean” diets than a low-fat diet (Shai I, Schwarzfuchs D, Henkin Y, Shahar DR, Witkow S, Greenberg I, Golan R, Fraser D, Bolotin A, Vardi H, Tangi-Rozental O, Zuk-Ramot R, Sarusi B, Brickner D, Schwartz Z, Sheiner E, Marko R, Katorza E, Thiery J, Fiedler GM, Blüher M, Stumvoll M, Stampfer MJ. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008 Jul 17;359(3):229-41.)
ABSTRACT
Background Trials comparing the effectiveness and safety of weight-loss diets are frequently limited by short follow-up times and high dropout rates.
Methods In this 2-year trial, we randomly assigned 322 moderately obese subjects (mean age, 52 years; mean body-mass index [the weight in kilograms divided by the square of the height in meters],31; male sex, 86%) to one of three diets: low-fat, restricted-calorie; Mediterranean, restricted-calorie; or low-carbohydrate, non–restricted-calorie.
Results The rate of adherence to a study diet was 95.4% at 1 year and 84.6% at 2 years. The Mediterranean-diet group consumed the largest amounts of dietary fiber and had the highest ratio of monounsaturated to saturated fat (P<0.05 for all comparisons among treatment groups). The low-carbohydrate group consumed the smallest amount of carbohydrates and the largest amounts of fat, protein, and cholesterol and had the highest percentage of participants with detectable urinary ketones (P<0.05 for all comparisons among treatment groups). The mean weight loss was 2.9 kg for the low-fat group, 4.4 kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group (P<0.001 for the interaction between diet group and time); among the 272 participants who completed the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg, respectively. The relative reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group (P=0.01). Among the 36 subjects with diabetes, changes in fasting plasma glucose and insulin levels were more favorable among those assigned to the Mediterranean diet than among those assigned to the low-fat diet (P<0.001 for the interaction among diabetes and Mediterranean diet and time with respect to fasting glucose levels).
Conclusions Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions.
What’s most interesting about this is, despite the low-carb group not being restricted to a specific daily calorie intake like the Mediterranean and low-fat groups (1,800 calories per day for men, 1,500 for women), but rather limiting carbohydrates to 20 grams per day for the first two months followed by 120 grams per day, and despite being advised to choose vegetarian sources of protein, which are generally lower quality than animal sources, they had the greatest weight loss. Additionally, the low-carb group had the greatest increases in HDL and greatest decreases in triglyceride levels. The low-carb group also had the greatest decrease in the ratio of total cholesterol to HDL, nearly twice that of the low-fat group (20% versus 12%).
I am surprised the weight loss for each of the groups was so low based on the calorie and carbohydrate intake guidelines, and strongly suspect poor compliance, very sedentary subjects, or both. If the subjects were actually following the guidelines I expect the weight loss would have been far greater for all groups.
I am also disappointed the dietitians advised the low-carb group to choose vegetarian sources of protein, as I suspect better weight loss and at least equal improvements in lipid profiles had animal sources been chosen.
In any case, it is further proof of the benefits of a higher-protein, lower-carbohydrate diet and it’s viability as an alternative to high-carb, low-fat diets. I have consistently seen better results in my own training and with my personal training clients with higher-protein and lower-carbohydrate intakes.