There has been so much conflicting information on whether a low-fat diet is more effective for weight loss than a low-carbohydrate diet. The new diet regimens and diet books are leaning toward the low carbohydrate approach and low fat is becoming more a diet of the past. I found two studies on this topic with similar outcomes (a rarity in
A study of 307 obese people in the Annals of Internal Medicine 2010;153;147-157 entitled Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet, compared these two approaches as to their success in producing weight loss and maintaining the loss over time.
The low-fat diet provided 1200-1800 calories per day with 30% of their calories coming from fat. The low-carb diet did not cut calories, but instead carbohydrates were limited to no more than 20 grams a day for 3 months. After that they added 5 grams/day/week until a stable weight was maintained. Both groups were given a comprehensive lifestyle modification program.
Weight loss was about 11 kg at 1 year and 7 kg at 2 years. There were no differences in weight or body composition between the groups at any point of the study duration. The return to previous eating habits was high in both groups by the end of the study
In the second study, a meta-analysis of five randomized controlled trials with a total of 447 people found that there were no significant differences between the groups in weight loss after 1 year. However, the low carbohydrate groups had lower triglyceride levels and higher high density lipoproteins, HDL (the good kind) while the low-fat groups had lower total cholesterol and low-density lipoproteins, LDL (the bad kind). (Effects of Low-Carbohydrate vs Low-Fat Diets on Weight Loss and Cardiovascular Risk Factors, Archive of Internal Medicine, Vol. 166; Feb, 2006).
“It’s really hard for people to sustain a low-carb diet. They can stick with it for six months, but then you see a gradual return to baseline,” said lead study author Dr. Marion Vetter, medical director of the Center for Weight and Eating Disorders at the University of Pennsylvania. “Low-fat diets may be a little easier for people to stick with.” However, low-fat diets have been criticized in the past as people tire of bland foods without much flavor. Low carb diets do include more fat and protein that provide more satiety and help to curb hunger.
In the long run, a diet for weight loss should be based on personal preference, i.e. the individual should choose with guidance what kinds of foods they would eat in moderation. Health issues such as cardiovascular risk factors (high triglycerides, low HDL, high LDL should be considered as well as just desired weight loss. Calories should come from a balance of all the macronutrients – carbohydrates, fats, and proteins. The avoidance of a single food group or a single nutrient should be discouraged in order to encourage weight maintenance.