Doctor's Weigh In On Diet and Exercise

Gretchen Becker Health Guide
  • Writing in the February 8 issue of Focus, a Massachusetts General Hospital intern decries the lack of evidence for the beneficial effects of exercise.


    She and her fiance recently embarked on an exercise program. She went to the gym five days a week instead of four and also increased the duration of her workouts from 30 to 40 minutes. Her fiance got a lot of advice from a personal trainer and passed it along to her. "But wait!" She thinks. "Has this advice been confirmed by controlled peer-reviewed studies? Where is the evidence?"


    As a physician, she said she is accustomed to giving advice on the basis of such well-controlled peer-reviewed studies, and she wants to find such evidence for common advice given about exercise. She said she didn't find much.

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    But here's what struck me even more than the discussion about exericse: her advice on diet. She says she took a nutrition course in medical school and has "skimmed a few papers comparing various diets" since then.


    "I can summarize the extent of my knowledge from these efforts: Weight Watchers good; Atkins bad."


    Later she says it's difficult to give patients lifestyle advice. One reason is that they can do that on their own, and when the physician does try to give lifestyle advice, "patients rarely follow our advice to the letter, if at all."


    Well can you blame them? If all a physician remembers about nutrition is "Weight Watchers good; Atkins bad," is it any wonder patients don't follow their advice? Especially when that advice is bad!


    A recent poster on the Diabetes International mailing list says she was following an Atkins diet for low blood sugar and was slim and healthy. Then she changed physicians, and the new physician convinced her that "Atkins bad." She switched to "healthy" low fat, gained 150 pounds, and was diagnosed with type 2 diabetes.


    This is, admittedly, annecdotal, not a peer-reviewed controlled trial. But it illustrates that at least for some patients, "Atkins good."


    Studies of diets will always be difficult to interpret. It's likely that some people will do better on low-fat diets whereas others will do better on low-carb diets. When you have diabetes, the chances are pretty good that the low-carb diets will work better, but even that is not guaranteed.


    Insulin tells the body to store fat. The more insulin you have circulating in the bloodstream, the more fat you store. When you have type 2 diabetes, and insulin resistance, you have even more insulin than normal in the early stages of the disease.


    This increased insulin is so the muscle cells, which have become insulin resistant and need more insulin to get the same effect, can take up glucose for energy. But the fat cells may not be as insulin resistant as the muscle cells. This means the extra insulin is simply going to tell them to store more fat than usual. The result is that you get fat.


    Because it's carbohydrate that tells the beta cells to produce insulin, the more carbs you eat, the higher your insulin levels, at least until you "burn out" your pancreas and are producing hardly any insulin at all. And constantly snacking keeps your insulin levels high all day long.


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    If we're expected to take any dietary advice from our physicians at all, we need physicians who have a deeper understanding of nutrition than "this diet good; that diet bad." Getting harmful advice from a physician makes us cynical about their abilities in general, and we might also ignore good advice about getting screened for cancer or getting pneumonia or flu shots.


    Nutrition is complex, but so is general medicine. Anyone capable of getting an M.D. degree should be able to deal with the compexities of diets. Medical schools need to emphasize the importance of understanding the fine points of dietary advice. And physicians in training need to listen and remember.


    More of Gretchen's posts:


    Low-carb or not? Old Ideas and the ADA

    Type 1 vs. Type 2: Can't we all just get along?

    Need a new diet? A humorous take on diabetes diets





Published On: March 03, 2008