In a nutshell: The one you will maintain.
The Evidence
Johnston, B. C., Kanters, S., Bandayrel, K., Wu, P., Naji, F., Siemieniuk, R. A., ... & Jansen, J. P. (2014). Comparison of weight loss among named diet programs in overweight and obese adults: A meta-analysis. JAMA, 312, 923-933. doi:10.1001/jama.2014.10397
What did the meta-analysis look into?
This meta-analysis investigated weight loss on people who followed 3 known (named/ branded) dietary programs, for up to a year. The meta-analysis synthesized evidence from 59 studies, including 7286 overweight and obese adults.
The diets were:
(1) Low carbohydrate diets (Atkins, South Beach, and Zone)
(2) Low in fat diets (Ornish and Rosemary Conley)
(3) Eating “in moderation” (Biggest Loser, Jenny Craig, Nutrisystem, Volumetrics, and Weight Watchers).
Weight loss was measured at 6 months and 12 months of following the diet. The meta-analysis also investigated if the following 3 factors affected the weight-loss, in addition to the diets:
(1) Calorie restriction (<1800 calories per day)
(2) Following a specific exercise programme
(3) Receiving support during the course of the diet (attending group or individual support sessions with health professionals)
The dieters’ weight-loss was compared to that of people who followed no named diet or had received the usual weight-loss advice (“engage in physical activity, keep records of food and calories consumed, eat ‘healthily’, set specific plans, and exercise self-control”).
What did the evidence suggest?
At 6 months, people who followed all 3 known diets lost more weight than those who had followed no known diet, or had followed the ‘usual advice’. Low carbohydrate diets resulted in more weight loss (minus 8.73 kilos), as compared to all other diet programmes, but weight loss from low-fat diets was similar (minus 7.99 kilos).
At 12 months, weight-loss slowed down for all dieters. Both low fat and low carbohydrate diets were superior to “eating in moderation”, to following “usual advice”, or to adhering to a no-known diet. Low carbohydrate eaters lost 7.25 kilos, while low fat eaters lost 7.27 kilos. In addition, exercising was associated with more (but small) weight loss for all dieters throughout the 12 months, while receiving expert support was associated with more weight loss during the first 6 months only. Dieters who also restricted their calorie intake did not lose more weight at any time.
The take-home message
Low carbohydrate and low fat diets appear to be superior to other diets, and equally successful in losing weight over a period of 12 months. Engaging in exercise and receiving support may offer additional (albeit small) weight loss benefits. Therefore, both diets will result in noteworthy weight loss, as long as they are maintained for a minimum of 6 months. Broadly speaking, several diets will result in weight loss, for as long as they are maintained.
