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Published: September, 2008; Vol 5, Num 4

 

Study Compares Diets, Effects, Results

Wrestling with efforts to lose weight and strengthen their health, many people feel bombarded by the conflicting claims of various diet programs.   A new, two-year study that compared three popular diet plans reveals some of the strengths of each while also demonstrating the relative difficulty of maintaining any of them.

“Many weight-loss programs grab the spotlight through books and television,” says LHSFNA Management Co-Chairman Noel C. Borck, “but it is well-known that people who use them often end up gaining the weight back. Merely ‘going on a diet’ is not the answer. To maintain success and health, you have to develop a dietary lifestyle that is balanced, moderate and personally sustainable.”

The new study in the New England Journal of Medicine compared three plans: the low-carbohydrate diet (Atkins), the low-fat/restricted calorie diet (American Heart Association) and the restricted calorie diet (Mediterranean).

Health Improvements

All three diets reduced waistlines and improved blood pressure. 

All raised levels of high-density lipoprotein (HDL), the “good” cholesterol that your body needs. Surprising some critics, the low-carbohydrate diet – which allows a higher proportion of fat intake – showed the most improvement in HDL. None of the diets had any effect on LDL, the “bad” cholesterol (other reports – see, for instance, Lowering LDL Cholesterol Without Drugs - US News and World Report – suggest whole food, plant-based diets and regular exercise can cut LDL).

The low-carbohydrate diet also achieved the greatest reduction in triglycerides, the unhealthy fats that contribute to heart disease.

Weight Loss

All the diets lowered levels of the hunger hormone leptin, and all produced significant weight loss. The low-carbohydrate diet produced the sharpest weight loss over the first six months and held its lead as the others gained ground over the two-year study. At the end, those in the low-fat group lost an average of six pounds while the Mediterranean group lost almost eight pounds and the low-carbohydrate group ten.

Only 45 of the 322 moderately obese people in the study were women, but they lost the most weight on the Mediterranean diet, about 13 pounds over the two years. Speaking to the Washington Post, however, Meir Stampfer, one of the study’s co-authors, cautioned that the women’s sample was too small to draw reliable conclusions about their possible differences from men.

Dietary Lifestyle

Though one of the longest dietary intervals ever studied, two years is relatively short to declare success in a lifestyle transformation. However, in the study, 90 percent of the low-fat dieters were still with the plan after the full two years, compared to 85 percent on the Mediterranean diet and 78 percent on the low-carbohydrate program.

Perspective

Participants – employees at a research center in Israel – were randomly assigned to each of the three diet groups and attended group meetings throughout the study. They also met regularly with a dietician, and those who struggled received motivational telephone calls to help keep them on track. In addition, they ate their lunches (the main meal in Israeli culture) at the research facility’s cafeteria which prepared and labeled options consistent with each diet. However, participants were free to eat whatever they chose, both at work and outside. Participants were encouraged to eat healthy protein, including fish, chicken without skin and dairy products that are low in saturated fat.

The Mediterranean diet restricts caloric intake and fat but allows fruit, vegetables, whole grains, fish, yogurt, olive oil and wine. In the study, the Mediterranean and low-fat groups were limited to 1,500 daily calories for women and 1,800 for men. Fat was limited to 30 percent of calories in the low-fat diet and 35 percent in the Mediterranean. 

The low-carbohydrate diet has been controversial because it does not restrict caloric or fat intake. Instead, it restricts carbohydrates. In the study, this group had no caloric or fat limits but was restricted to 20 daily grams of carbohydrates for the first two months (equivalent to a slice and a half of whole grain bread) and then, a gradual increase to 120 grams. 

In some quarters, the low-carbohydrate diet is also known as the high-fat diet. Part of the appeal of the diet is that dieters can consume products like bacon or butter in specific proportions that are generally forbidden by low-fat diets. However, some dieters skip the plan’s “fine print.” Though fat is allowed, it must be part of a total caloric intake that does not exceed 1,500 – 1,800 daily calories for women or 1,800 – 2,000 for men, depending on body size, age and metabolism.  In this study, the low-carbohydrate group was encouraged to chose vegetarian sources of fat and protein.

Stampfer stressed the difficulty in sustaining successful weight loss, saying, “You can lose weight, but it is hard and it is not going to happen rapidly. You have to choose a diet that you can stick with for the rest of your life.” 

Regular exercise is also an important aspect of maintaining a healthy weight. Before starting any new diet or exercise program, be sure to consult with your health care provider. The LHSFNA has developed a Nutrition and Fitness for Laborers program for trainers. Two of the program’s pamphlets, Becoming Physically Active and Weight Matters are useful resources for Laborers and family members who want to achieve a healthy weight. They are available through the Fund’s online Publications Catalogue.

[Steve Clark]