Packaged food diets may spur more weight loss

May 14, 2013

A study published in the Journal of Obesity shows that people who eat a diet of portion-controlled packaged foods may lose more weight than those who only get nutritional advice.

The diet the researchers studied was the Medifast 5 & 1 Plan. It consists of five pre-packaged meals each day, along with one meal of vegetables and protein prepared by the dieter. Dieters can pick from 70 different packaged foods to create five meals totaling about 1,000 calories a day. People on the plan can also purchase different levels of support along with the meals, such as access to dieticians and recipes.

To see how effective the Medifast diet is in helping people lose weight and keep it off, the researchers asked 60 people to join the plan for free. They compared these dieters to another 60 people who were given advice on how to meet a 1,000 calorie-per-day target, but who continued to buy and prepare their own food. For everyone in the study, the goal for the first 26 weeks was to lose weight, and during the second half of the study the goal was to maintain weight. All of the participants were obese, having a body mass index (BMI) between 35 and 50. By the end of the study, 15 people dropped out of the regular-food group and 10 dropped out of the Medifast group.

After six months, those in the Medifast group lost an average of 16.5 lbs, or 6.7% of their starting weight. The regular-food group lost an average of 8.4 lbs, or 3.4% of their body weight. The Medifast dieters also had greater reductions in body fat, waist circumference, and cholesterol than the other group. The study did not examine the diets’ effects on bone and muscle mass.

Over time, though, the dieters in both groups tended to rebound somewhat toward their original weights. After one year in the study, the Medifast group ended up about 10 lbs, or 4.2%, lighter than when they started, while the other group was about 4 lbs, or 1.7%, lighter.

James Shikany, the lead author of the study, said the results show that sticking to the Medifast diet makes it harder for dieters to eat more calories than they should. “It’s more of a regimented type of diet, and some people find that’s what they need in order to limit their portion intake,” said Shikany, Professor at the University of Alabama at Birmingham Division of Preventive Medicine.