Healthy, Low-Fat Diet? Maybe Not

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Healthy, Low-Fat Diet? Maybe Not
Recent studies throw conventional diet recommendations about fat and diabetes into question.

By Jimmy Moore

For the past three decades, dietary conventional wisdom has been to eat a low-fat (high-carbohydrate) diet in order to best manage your weight, lower your cholesterol, reduce your blood pressure, and improve overall health.

However, surprising results coming out of modern-day research labs are challenging many of these long-held beliefs regarding what constitutes a healthy diet. It’s beginning to look like we’ve been careening down the wrong path all this time, and what you think you know about dietary fat and diabetes, in particular, may be quite a bit off the mark. Here are just a few of these findings:

High-carb diet elevates triglycerides, lowers HDL (“good” cholesterol). According to a study published in the January 2007 issue of the American Journal of Clinical Nutrition, researchers recently examined the diets and cholesterol levels of various groups in Canada to look for associations between carbohydrate intake and HDL cholesterol and triglyceride levels. Those study participants who consumed the highest amounts of carbs exhibited lower levels of HDL cholesterol and higher triglyceride levels. The group that consumed more carbohydrates than any of the others, overall, had the lowest levels of HDL cholesterol.

High-carb diet ineffective for people with high insulin levels. Researchers at Children’s Hospital in Boston conducted a randomized trial in which participants spent six months on either a low-glycemic-load diet or a low-fat, high-carb diet and were then followed up for a year. Those with higher concentrations of insulin fared much better on the low-glycemic-load diet than on the high-carb one. The study showed the low-glycemic-load group lost five times more weight after 18 months and nearly three times more body fat than the low-fat, high-carb group. This study was published in the May 16, 2007, issue of the Journal of the American Medical Association.

High-carb diet increases insulin levels which spikes blood pressure. In an analysis of 10 intervention studies comparing the high-carb, low-fat Dietary Approaches to Stop Hypertension (DASH) diet with a low-carb, high-monounsaturated fat diet, researchers wanted to see what effect the different diets would have on blood pressure separate from the benefits of any weight loss. What they found was that the high-carb, low-fat diet produced significantly higher blood pressure than did the low-carb, high-monounsaturated fat diet. The study was conducted by researchers from the University of Texas Southwestern Medical Center, and published in the May 2007 issue of The American Journal of Clinical Nutrition.

High-carb diet leads to greater risk for age-related macular degeneration (AMD). A Tufts University study of nondiabetic seniors looked at the role of diet on AMD and found that those study participants who consumed a higher-carb diet had a 49 percent increased risk for developing advanced AMD. The researchers concluded that 1 in 5 cases of advanced AMD could have been prevented entirely by consuming a lower-carb diet. This study was published in the July 2007 issue of the American Journal of Clinical Nutrition.

Jimmy Moore is the author of the weight-loss, health blog, Livin' La Vida Low-Carb.

SOURCES:

1 - Anwar T. Merchant et al., "Carbohydrate intake and HDL in a multiethnic population," The American Journal of Clinical Nutrition 85, no. 1 (January 2007), http://www.ajcn.org/cgi/content/abstract/85/1/225 (Accessed November 17, 2007).

2 - Cara B. Ebbeling et al., "Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults," Journal of the American Medical Association 297, no. 19 (May 16, 2007), http://jama.ama-assn.org/cgi/content/abstract/297/19/2092 (Accessed November 17, 2007).

3 - Meena Shah et al., "Effect of high-carbohydrate or high-cis-monounsaturated fat diets on blood pressure: a meta-analysis of intervention trials," The American Journal Of Clinical Nutrition 85, no. 5 (May 2007), http://www.ajcn.org/cgi/content/abstract/85/5/1251 (Accessed November 17, 2007).

4 - Chung-Jung Chiu et al., "Association between dietary glycemic index and age-related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study," American Journal of Clinical Nutrition 86, no. 1 (July 2007), http://www.ajcn.org/cgi/content/abstract/86/1/180 (Accessed November 17, 2007).



Reviewed by Susan Weiner, R.D., M.S., C.D.E., C.D.N. 3/08

 

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