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Midriff to midriff: Is the low-fat diet going belly up?


A study recently published in the New England Journal of Medicine reminds me of the old joke, “Want to lose 10 pounds of ugly fat? Chop off your head.”

Yes, some weight-loss strategies are healthier than others. And when it comes to dieting, the question is, do you want to lose weight, or get healthy, or both? In other words, are some weight-loss diets healthier than others?

Of course there are a million dietary approaches to losing weight, many of them bizarre and cult-like, but practically speaking there are three main contenders: the low-fat diet, the Mediterranean diet and the low-carbohydrate (Atkins) diet. For a two-year period, the New England Journal study put these three diets head to head, or shall we say, midriff to midriff.

The low-fat diet is the aging veteran, touted by the likes of the American Heart Association. It lives up to name, emphasizing 1,500 daily calories for women and 1,800 for men, with only 30 percent of total calories coming from fat. If, like Americans of yore, you like your meat red and marbled, the low-fat diet tends to be a “high-carbohydrate” diet by simple deduction, since your main protein source — corn-fed beef — is locked up with a lot of saturated fat.

On the opposite end of the spectrum is the Atkins diet, the oddball all-you-can-eat diet that despises carbohydrates. Known as the steak ‘n’ bacon diet, the Atkins diet is perhaps more sophisticated than its public image, encouraging vegetarian sources of fat and protein.

In the middle is the Mediterranean diet, a diet defined by a region and its flora and fauna: plenty of olive oil, nuts and vegetables, with smaller amounts of fish and chicken mixed in.

This Israeli study recruited 322 moderately obese (Body Mass Index of 31 — here’s how to calculate your own) workers in a single facility and randomized them to one of three diets. Participants got a lot of support from dietitians, including in the cafeteria at lunch, the main meal for Israelis. With the caveat that participants in any study tend to outperform their lay counterparts (because they know they’re being watched), here are the numbers for the biggest losers:

In terms of weight loss, the Atkins diet came in first, with a mean weight loss of 10.4 pounds; followed by the Mediterranean diet at 9.7 pounds, and the low-fat diet at 6.4 pounds. Interestingly, adherence rates for the individual diets — who could actually stick with the plan — ran in the opposite order: 90 percent stuck with the low-fat diet, 85 percent with the Mediterranean, 78 percent with Atkins. That’s in spite of the fact that the Atkins diet has no calorie restrictions, and, at least in theory, the lowest hunger pangs. When the body has no carbohydrate to burn, it shifts its metabolism and generates a substance called ketones, a proven appetite suppressant.

There were some ways in which the diet plans were quite equal. All participants had their maximum weight loss in the first six months, and they all had similar decreases in waist size and blood pressure. Caloric intake also dropped a similar amount for all three groups, which raises the question: If they all had similar calorie reductions, why did some groups lose more weight than others? This conundrum — is a calorie a calorie, no matter what its food form? — has yet to be solved by the nutrition community. For this study, it appears that some food calories burn more efficiently than others.

Trimmer, yes, but healthier on the inside?
Returning to the question of whether some weight loss is healthier than others, the choice of diet didn’t seem to affect the dieter’s bad cholesterol (LDL), but it did seem to matter to the HDL, the good cholesterol. HDLs went up 8.4 mg/dL with the Atkins diet, but rose only about 6.3 mg/dL for both the Mediterranean and low-fat diet. That’s in line with one of the metabolic surprises from the Atkin’s diet: that a diet with no limits on protein and fat can actually buff up one’s cholesterol profile.

Besides measuring cholesterol, the researchers also checked other biomarkers in the blood. If you read my piece on Tim Russert’s death, you’ll know that the problem in atherosclerosis (heart disease) isn’t so much that the arteries are clogged, it’s that they’re inflamed; and it’s this inflammation that leads to scarring and narrowing. C-reactive protein is a marker for measuring body-wide inflammation, and CRP levels fell more sharply for those on the Mediterranean or Atkins diet than they did for the low-fat group. Could a pound lost on the Atkins or Mediterranean diet be more soothing to aching arteries than a pound lost on the diet recommended by the American Heart Association? Perhaps so.

The blood work also showed that the Mediterranean diet seemed to have the most beneficial effects for those participants who were diabetic, significantly lowering their fasting glucose levels, which actually increased on the low-fat diet. It’s a finding that might be explained by monounsaturated fats’ (found in high amounts in olive oil) ability to improve the function of insulin in the body.

Sex changes everything

The study also shows that your mother was right: Sex complicates everything. Eighty-six percent of this study’s participants were male. For females, the weight-loss patterns looked quite a bit different. Mean weight loss was highest for the Mediterranean diet (13.6 pounds), then the Atkins (5.3 lbs), with the low-fat diet barely flicking the needle (0.2 lbs).

Linda Brady is professor of nutrition at the University of Minnesota. Keeping in mind that the number of women in the study was small, she was not surprised to find that there might be gender differences.

“There are differences in enzymes and fat distribution and the hormones — and I don’t know if the hormones are driving it — but certainly in terms of where your fat gets deposited, there are differences in men and women and how it’s mobilized,” Brady explained. “And we know that men and women burn fuels very differently in exercise in terms of how much carb and how much fat,” she added. “So it doesn’t sound like it’s out of this world in terms of a conclusion, although you’d want some more data.”

What to make of this latest diet study

First, an apology. It’s embarrassing to me as a physician that we’ve developed a health care system that has come up with some spectacular treatments for spectacularly rare illnesses, and yet we still don’t know what to eat.

One thing’s for sure: The low-fat craze has left us fatter than ever, and as this study —and others — have suggested, avoiding fat may not be the best way to become less fat. Or, more healthy. Brady agrees.

“The party line would be, well, fat is much more efficient to put into fat than carbohydrate is, and so it should make you fatter,” Brady explained. “And that’s kind of the way people have explained the whole [low-fat diet] idea, but…,” Brady trailed off. And here comes the very big but: The science isn’t supporting the party line, or our nation’s waistline.

“The fact is that Americans have decreased their fat intake over the last ‘x’ number of years, and we’re more obese than ever. There is something going on, and that’s where I really get upset with the nutrition field, because this is crazy. All these things we’ve done and the millions of dollars we’ve spent in grant money, and yet we’re fatter than ever. What’s going on here,” Brady asked.

If anyone should know what’s going on, it’s Dr. Walter Willett. He’s the chair of the department of nutrition at Harvard School of Public Health, and arguably our country’s Dean of Diets. As Willett suggested in a recent interview in Time, we’d all be healthier if we stopped dieting and just ate reasonable amounts of what we know to be healthy foods. Forget the focus on limiting carbs vs. fat.

“We’ve looked at over 250,000 men and women for up to 30 years, and we [also] haven’t seen that the percentage of calories from fat or carbohydrates in your diet makes any difference in relation to heart attacks, various cancers, or strokes,” Willett told Time.

As Willett points out, it seems that total carbs and total fats aren’t so important. But the kind of fat is very important, as saturated fats and trans fats are bad for diabetes and heart disease, whereas unsaturated fats are actually protective.

“It’s the same with carbohydrates,” Willett told Time. “The total amount is not important. But high intake of refined starch and sugar is related to a higher risk of heart disease and diabetes, whereas high-fiber whole grain carbohydrates are related to a lower risk.”

So ditch the diet. Eat healthy foods — including healthy fats — in healthy portions.

Dr. Craig Bowron is a Twin Cities internist and writer who reports on medical topics for MinnPost. He can be reached at cbowron [at] minnpost [dot] com.

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Comments (5)

  1. Submitted by Matt Lisk on 07/28/2008 - 06:48 pm.

    It is refreshing to see a member of the medical community finally acknowledging what the fitness community has already proven – in order to lose fat you need to eat fat! The diets of my clients rely on red meats, fish and/or fish oils, avocados, eggs, nuts and other sources of mono- and poly-unsaturated fats. The proof is not only in their waistlines but also in their bloodwork!

  2. Submitted by Duke Powell on 07/29/2008 - 08:10 am.

    Eight months ago my weight was 240, waist was 43 and the blood work was awful. Blood pressure borderline high.

    I went on a low carb diet. Eggs, sausage, hamburger, steak, cheap cuts of red meat, salmon, tuna, mountains of spinach, brocolli, cauliflower, cheese, berries, almonds and oceans of butter make up the bulk of what I eat. Carbs are generally limited to sauces.

    Results, lost 50 pounds between Thanksgiving and April and have now settled at 190 pounds. Waist is now 36, blood pressure yesterday was 110/64 with a resting pulse of 64.

    I have not exercised a lick.

    I don’t call this a diet. It is something that I will do for the rest of my life.

  3. Submitted by NIcole Masika on 07/28/2008 - 02:27 pm.

    From a former dietitian: It’s been a while since I figured out white flour and refined sweeteners are more of problem than how much fat you eat. But is it ever hard to avoid those things! I think that is the appeal of Atkins, it simplifies that problem by avoiding carbs, but I think it does have lot of potential to be unbalanced and unhealthy because of that.

    I wonder how long it will be before I can easily find a sandwich on whole grain bread near my workplace? There are lots of wonderful, otherwise healthy looking sandwich choices in the nearest shop, but they are on white buns, white foccacia, white tortillas.

  4. Submitted by Bernice Vetsch on 07/28/2008 - 12:23 pm.

    Can a study involving only one mostly-male ethnic group be considered to apply to the diverse American population? Should American researchers replicate it with a larger group, one-half female and including members of various ethnic and racial groups?

    Did this study monitor the amount of exercise participants took part in?

    Dr. Atkins himself cautioned those who tried his diet to follow it for no more than two weeks at a time. Is his advice now proved to be wrong?

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