A low-fat, high-fiber diet led to significant weight loss in diabetics.
The best foods for diabetes control have been a subject of controversy. A few scientists have espoused high-monounsaturated fat diets because, they argue, low-fat, high-carbohydrate diets may have negative consequences like higher triglycerides.
But long-term studies and an important new research have found just the opposite. The research has reported that a low-fat, high-fiber carbohydrate diet led to significant weight loss in diabetics; a high-monounsaturated fat diet did not. Moreover, the low-fat, high-fiber carbohydrate diet did not cause any unfavorable blood lipid reactions, such as higher triglycerides or worsening of glycemic control.(1)
Dr. William E. Connor and colleagues from Oregon Health & Sciences University in Portland, Oregon, randomly assigned 11 patients with type 2 diabetes to receive an ad libitum (eat-as-much-as-you-want) low-fat, high-fiber, high-complex carbohydrate diet or an ad libitum high-monounsaturated fat diet, each for 6 weeks.
The low-fat diet provided 20% calories from fat and was largely made up of fruits, vegetables, whole grains, beans, skim milk, and lean meat, very similar to the Pritikin Eating Plan. The dieters used condiments like fat-free Italian dressing and fat-free sour cream.
The high-fat dieters (40% calories from fat) consumed full-fat foods like olive oil and safflower oil and ate fewer fiber-rich carbohydrates (30 grams of fiber daily vs 46 on the low-fat, high-fiber diet).
“The most striking finding in this study was that the ad libitum low-fat, high-fiber diet induced a significant weight loss, whereas the high-mono fat diet did not,” writes Dr. Connor and co-authors. Why? Patients assigned to the low-fat diet ate 212 fewer calories than did those assigned to the high-monounsaturated fat diet.
For diabetics, getting and staying lean is critical. “Losing excess body fat remains the most effective way to prevent and treat type 2 diabetes,” notes Dr. James Kenney, Nutrition Research Specialist at the Pritikin Longevity Center & Spa.
In the study from Oregon, the low-fat, high-fiber diet did not raise triglycerides and worsen glycemic control, as some studies have concluded. But these studies, point out the Oregon researchers, did not mimic real-world environments. Subjects were forced to eat the same number of calories on high-carbohydrate diets as they had on high-fat diets. Never did they have the opportunity to evaluate how full they were – and how much of the foods on the differing diets they preferred to eat.
Invariably, whenever real-world eating (letting subjects decide how much they want to eat) is part of a study’s design, as with this research from Oregon, people eating low-fat diets rich in natural, high-fiber foods like fruits, vegetables, and whole grains lose weight. With weight loss comes a wealth of other benefits, including lower triglycerides, lower LDL (bad) cholesterol, lower blood pressure, and increased protection against diabetes and cardiovascular disease.
Spontaneously, the diabetics in the Oregon investigation consumed fewer calories on the low-fat diet than on the high-fat diet because the calorie density (the number of calories packed into a given weight of food) was lower on the low-fat diet. Water-rich, fiber-rich carbs like fruits, vegetables, beans, and whole grains provide a lot of stomach-filling food, but not a lot of calories. “Many of our subjects,” notes Dr. Connor, “expressed the sensation of ‘fullness’ during the low-fat diets.”
Conversely, with foods of high calorie density, like those rich in sugar, oil, and other fat, people are likely to eat more calories just to get in a satisfying amount of food. What fills you faster? One tablespoon of corn oil or two large ears of corn? Both are equal in calories but worlds apart, certainly, in their ability to satisfy hunger.
Other research on diets has netted similar results. In a six-month study, overweight people with the metabolic syndrome following a low-fat, high-complex carbohydrate diet lost weight and lowered triglycerides.(2) In two long-term trials of people with impaired glucose tolerance, the Finnish Diabetes Prevention Study(3) and the US Diabetes Prevention Program(4), decreasing dietary fat and increasing fiber-rich foods and physical activity led to more weight loss than the control group and about a 60% reduced risk of developing diabetes.
“No comparable data exist demonstrating that higher-fat diets slow the progression of impaired glucose tolerance to full-blown type 2 diabetes,” asserts Dr. Kenney.
Bottom line: “In studies of free-living people, those in which people – not scientists – control how much they eat, the best foods for diabetes control are those that are low in fat and high in unrefined carbohydrates. They have been shown repeatedly to promote weight loss, improve blood lipids, and reduce the risk of developing type 2 diabetes and cardiovascular disease,” states Dr. Kenney.
“By contrast, diets with more fat and fewer carbohydrates will generally be more calorie dense and lower in fiber and, as a result, less likely to lead to weight loss – and less effective, then, in preventing the development of type 2 diabetes and cardiovascular disease in the long term.”
1. American Journal of Clinical Nutrition, 2004; 80: 668.
2. American Journal of Clinical Nutrition, 2002; 75: 11.
3. New England Journal of Medicine, 2001; 344: 1343.
4. New England Journal of Medicine, 2002; 346: 393.