Which Diets Work? A Side Order of Perspective

Michael J. Joyner, MD

October 13, 2014

Reevaluating the Healthy Diet

What constitutes a healthy diet? Until about a month ago, the conventional wisdom told us that a healthy diet was low in fat and salt, and involved eating breakfast. Since that time, the news has reminded us (or perhaps re-reminded us) that it is not that simple. A recent, widely reported study showed that low-carbohydrate (carb) diets might be better.[1] Before that, we heard that either too much or too little salt in the diet can be bad,[2] and before that we heard that skipping breakfast may not be so bad after all.[3]

All Diets Can Work; Most Don't

Before anyone switches to a low-carb diet, it is important to remember that all diets can work in the short run. However, most diets fail in the long run,[4] and sticking with a diet is far more important than whether the diet is low-carb or low-fat.

If you look at people who lose a lot of weight and keep it off over many years, a consistent pattern emerges.[5] When more than 10,000 real-life "biggest losers" (people who have lost at least 30 lb and kept it off) were surveyed, most succeeded by doing a few simple things:

78% eat breakfast;

75% weigh themselves regularly;

62% watch less than 10 hours of TV per week;

90% exercise about 1 hour per day; and

Most eat a low-calorie, low-fat diet.

Among the weight regainers in this study,[6] reductions in leisure-time physical activity, dietary restraint, and frequency of self-weighing and increases in percentage of energy intake from fat and disinhibition (less self-control) were associated with greater weight regain.

The advocates of low-carb diets will come back and say, "But the new study is a randomized clinical trial!"—and thus it should trump the observational data. A bigger randomized clinical trial[7] that followed weight loss in about 5000 patients with type 2 diabetes for 8 years showed that those who lost 10% of body weight and kept it off for 8 years did pretty much the same thing:

[P]articipants who at year 8 maintained the ≥10% loss versus [those who[ gained above baseline weight revealed that maintainers reported higher activity-related energy expenditure (about 1500 vs 800 calories per week) and a greater number of weeks in the prior year reducing their calorie and fat intake. Weight [loss] maintainers also were more likely than full regainers to weigh themselves daily or more often....

What About Salt?

The news about salt is hardly surprising. It has been known for years that blood pressure is salt-sensitive, but only in some people. The risks associated with excessively low-salt diets have also been known for years.

However, determining exactly who is salt-sensitive can be difficult, and the biggest problem from a population health perspective is too much salt leading to high blood pressure, stroke, and heart disease. Public health guidelines are sometimes blunt instruments, and given the overwhelming link between too much salt and bad outcomes,[8] it is probably acceptable that the guidelines are straightforward and even oversimplified.

Before You Skip Breakfast

Before you start skipping breakfast, keep the data from the real-life biggest losers in mind. They tend to eat breakfast. Also, the classic epidemiologic studies by Lester Breslow, who lived to age 97 in good shape, suggest that eating breakfast helps people live long and healthy lives.

The Conventional Wisdom Lives On

Medical guidelines and evidence come and go and are subject to regular revision.[9] However, sometimes the newest findings lead people to jump on bandwagons related to the latest and greatest studies, when a longer view might be helpful. In the case of diet, this is amplified by public anxiety, along with pitchmen and others promoting diets with magical properties that melt the pounds away and make them better than any alternative.

However, before you adopt a high-fat diet, stop worrying about salt, and start skipping breakfast, keep the long-term outcome data in mind. So far, they have stood the test of time. Of greater importance, if you want to lose weight and keep it off, recognize that you are going to have reengineer your life by eating less, exercising more, weighing yourself regularly, and turning the TV off. Unfortunately, there are no magic bullets.


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