Health met physics in last week's New England Journal of Medicine with a study revealing that the type of diet doesn't matter so much for weight loss — be it low-fat, low-carb, 70-percent yak meat or whatever — as long as one simple requirement is met: Consume fewer calories than you burn.
The discovery harkens back to the Age of Enlightenment and the law of conservation of energy, a concept lost in the fad-diet world for the last 200 years.
That said, not all diets are created equal. This latest health study, led by Frank Sacks of Harvard School of Public Health, does not exonerate any particular diet, as some news reports have implied. The reason is that diets should not be simply about losing weight.
Looking good in spandex is one thing; having healthy organs and a cardiovascular system is other. Fad diets tend to fail you with the latter.
Trinity of macronutrients
Many diets concentrate on what are known as macronutrients: protein, fat and carbohydrates. These contribute to nearly all of your daily calories, with the rest filled in by micronutrients — vitamins and minerals and other nutrients — plus dietary fiber, which often is lumped in with carbohydrates.
The Harvard-led study was a relatively large and methodologically sound clinical trial that followed about 800 overweight adults for two years. This group was placed on one of four kinds of diets, ranging from moderately low-carb and high-fat to high-carb and low-fat.
Regardless of the macronutrient ratios, the patients lost the same amount of weight, about 13 pounds after one year but a total of about 8 pounds at the end of two years.
The study's strengths are the size, duration and the systematic approach to uncover the reason for the mixed reports from other health studies concerning the efficacy of this diet versus that diet. There's never a final word when it comes to health studies, but this Harvard study is pretty close.
The study's weakness was the failure to keep patients faithful to their particular diet. But then again, this could be another strength, because this is the real world and emphasizes the problem with fad diets.
Ever defensive, Atkins Nutritionals issued a rebuttal to the Harvard study a day after its publication, claiming that the low-carb ratios used in that study doesn't come close to the levels Atkins recommends. This claim is true, of course, in all its classic Atkins irony.
The Harvard study dipped as low as 35 percent for calories derived from carbohydrates (with a corresponding fat level of 40 percent). The first phases of the Atkins diet recommends that only 10 to 25 percent of calories are derived from carbohydrates. The problem is that many health experts view these levels to be unhealthy.
The World Health Organization recommends a range of 50 to 70 percent of calories come from carbohydrates. Ten percent carbohydrates is the bare minimum needed to prevent severe ketosis, a condition in which the blood becomes abnormally acidic from ketones, the byproduct of burning fat for fuel instead of glucose.
The Harvard-led group, comprising heart experts, nutritionists and biostatisticians, had its standards: The diets needed to include 8 percent or less of saturated fat, at least 20 grams of dietary fiber per day, and 150 mg or less of cholesterol per 1,000 kcal. The Atkins diet, the group determined, wasn't conducive to that.
Real world dieting
To be fair, the same is true about extreme low-fat diets. In the real world, these are hard to follow and become dangerous. In the Atkins regime, there is the temptation to sway from the precise Atkins recipe for success (which has changed over the years) and to consume protein high in saturated fat, cholesterol and salt, which are all treacherous for cardiovascular health.
In extreme-low-fat diets there is the temptation to consume simple carbohydrates instead of complex carbohydrates, which raises the risk of insulin intolerance and diabetes.
The most sensible diet for total body health — for weight maintenance and organ and joint health — remains to be low in fat and high in complex carbohydrates mostly derived from plants, despite our hunger for fast results from fad diets.
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Christopher Wanjek is a Live Science contributor and a health and science writer. He is the author of three science books: Spacefarers (2020), Food at Work (2005) and Bad Medicine (2003). His "Food at Work" book and project, concerning workers' health, safety and productivity, was commissioned by the U.N.'s International Labor Organization. For Live Science, Christopher covers public health, nutrition and biology, and he has written extensively for The Washington Post and Sky & Telescope among others, as well as for the NASA Goddard Space Flight Center, where he was a senior writer. Christopher holds a Master of Health degree from Harvard School of Public Health and a degree in journalism from Temple University.