To lose weight, almost any of the popular diets will do. Most tout a particular balance of macronutrients, that is, protein, fats, and carbohydrates. But research by the U.S. Department of Agriculture (USDA) suggests these diets work mainly because they reduce calorie intake.
Most published research has focused on the amount of weight lost, without addressing the long-term effects of various eating plans. Are these diets healthy? And will they keep the weight off? It’s still unclear whether macronutrient juggling is a good way to control weight long-term. But some studies—including comparative data from the USDA—offer clues.
Types of Diets
The USDA divided popular diets into three categories. Researchers found that, without physical activity and regardless of food composition, a diet containing 1,400-1,500 calories per day takes off weight. All of the diets they studied resulted in calorie intakes in this range.
More Lost Than Just Weight
A healthy diet includes a mix of foods from all food groups. Other eating plans require supplementation. For example, because people who follow very-low-fat diets eat less meat, they may be short of zinc, iron, vitamin E, and vitamin B12.
The American Heart Association (AHA) recently issued a scientific advisory warning that high-protein diets that include large amounts of meat are potentially dangerous because they may increase the risk for heart disease, diabetes, stroke, kidney and liver disease, and cancer. High-protein diets also severely limit the intake of fruits, vegetables, and whole grains—all sources of important minerals and vitamins.
Weight Control Over Time
Anyone who’s tried to lose weight knows that losing it isn’t as hard as keeping it off. We need further research on long-term weight control, but data from successful dieters offer a glimpse of what it takes. The National Weight Control Registry is a database of people who maintained a minimum weight loss of 30 pounds for more than 5 years. Most had become overweight before age 18. Here are some of their strategies:
• To lose weight, most (89%) modified both dietary intake and physical activity. They also weighed themselves frequently.
• 88% limited certain types of foods, 44% reduced portion size, and 44% counted calories. Most also made sure they ate breakfast.
• To maintain weight loss, most (92%) limited certain foods, 49% limited the percentage of calories from fat, 36% counted calories, and 30% counted fat grams.
• The average marcronutrient balance of successful dieters was 24% fat, 56% carbohydrates, and 19% protein.
• The women reduced their caloric intake to about 1,300 calories a day and expended about 2,700 calories a week (the equivalent of walking about 28 miles) through one or two types of exercise.
Physical Activity is Key
We all know that physical activity, even something as simple as walking, is good for us. It may also determine if you’re a “maintainer” or “gainer” in the weight-control stakes.
Researchers at the University of Alabama carried out a one-year follow-up of 47 women, ages 20-46, who were initially in the normal weight range (a body mass index of less than 25).
The scientists found that the weight maintainers were 44% more physically active than the weight gainers, who put on 21 pounds, on average. Testing at the beginning and end of the year suggested that the main difference between the groups was that the maintainers engaged in more low-intensity daily activities, such as walking, climbing stairs, or gardening.
In fact, the researchers concluded that 77% of the gainers’ added poundage reflected a lack of such daily activity, rather than dietary or metabolic factors.
Official guidelines suggest that expending about 1,000 calories per week on physical activity offers important health benefits. That level is probably insufficient, however, for weight loss or preventing weight gain after weight is lost. Women in the National Weight Control Registry burned almost three times that amount.