“Low Fat” Comes in Last Place… Again

So three penguins walk into a bar, get to talking, and decide to enroll in a diet study.

I’m kidding of course, but I thought it might be a novel way to introduce the new diet study that was just published in the august Journal of the American Medical Association, and has got the media all a dither.

It’s actually a pretty good study, and there’s even been some truthful and accurate reporting on it, a rarity in an age when simplistic sound bites substitute for careful analysis. But in case you missed reading about it, here’s what you need to know, starting with the back story.

See, The conventional wisdom is that all calories are calories, that it doesn’t matter where they come from, and that weight loss is essentially about “calories in, calories out”. It’ called the “energy balance” theory; you take in calories through food, you burn up calories through activity, and if you “burn” more than you take in, you lose weight. If, on the other hand, you take in more than you burn up, you gain weight. Period.

We’ve been hearing this same old past-its-expiration-date claptrap about all calories being equal for decades now. I won’t name names (American Dietetic Association) but lots of mainstream organizations and health authorities have been parroting this “a calorie is a calorie” stuff to us for years. They’re still doing it.

The researchers decided to see if it were true.

Spoiler alert: it’s not.

The researchers in this study wanted to specifically look at the metabolic effects of different diets composed of the same number of calories. They wanted to see if varying the amount of protein, fat or carbs impacted important metabolic markers, like, for example, how many calories you burn at rest.

Remember—the holy grail of “diet” programs, the promise of every infomercial, is the ability to “boost your metabolism”. Burning more calories at rest—and burning more calories, proportionately, when you’re active—is the very definition of a “boosted” metabolism, isn’t it? The researchers wanted to see if, for example, a high-protein diet caused people to “burn” more calories than, say, a low-fat diet, even if calories were kept the same.

So what happened?

Let’s go to the videotape.

Researchers first took 21 participants, age 18-40, and put them on a variation of the Zone diet, feeding them 45% carbs, 30% fat and 25% protein. All of them lost between 10-15% of their body weight over the course of three months. So far, so good.

A month later, the participants were placed on one of three diets for a month.

  1. A low-fat diet (fat= 20% of calories)
  2. A low-carb diet modeled on Atkins (10% of calories from carbs)
  3. A low-glycemic diet (40% carbs, 40% fats and 20% protein)

(Note: low-glycemic means that all the foods had minimal impact on blood sugar; essentially that means a very low-sugar diet with minimal amounts of processed carbs like cereals and breads. Processed carbs have the most dramatic effect on blood sugar, which, in turn, raises levels of the fat-storage hormone insulin, making it really easy to gain weight.)

Participants were switched around so that every person ultimately went on each of the three diets for one solid month.

Ready for the results?

The low-fat diet had the worst effect on calorie burning.

Low-fat dieters also had increases in triglycerides—a major risk factor for heart disease—and had decreases in protective HDL cholesterol. “The low-fat diet that has been the primary approach for more than a generation is actually the worst for most outcomes, with the worst effects on insulin resistance, triglycerides and HDL, or good cholesterol, said David Ludwig, MD, lead researcher on the study.

In other words, the low-fat diet stunk.

(No news to readers of this newsletter, but I digress.)

The group that had the greatest increase in “energy expenditure” (calories burned)? The low-carb group.

The low-carbers actually boosted their metabolism by a whopping 350 calories a day compared to those on the low-fat diet, approximately the same as an hour of moderate exercise. And the low-glycemic dieters did pretty well also, burning 150 calories more per day than those following the god-awful low-fat diet.

The news wasn’t all good for low-carbers, however. The extra calories burned came at a cost. Those on the low-carb diet had higher levels of CRP- a measure of systemic inflammation—and higher levels of cortisol, the major stress hormone in the body. Those on the low-glycemic diet did not have any of those negative results.

I’m a huge fan of David Ludwig, one of the smartest and least biased researchers working in the field of weight loss. And I can certainly see why he concluded that, all things considered, the low-glycemic diet is the way to go. You still get a huge bump in metabolism, but no negatives to go along with it.

My only question here is why the low-carbers saw their CRP and cortisol levels rise. It’s tempting to think it’s simply the low-carb diet, but I’d want to know more specifics.

For example, the low-carbers were on a diet of 40% fat. I’m guessing most of that fat was vegetable oil, the kind we’ve been taught is so “healthy” but is actually quite pro-inflammatory. (That could have accounted for why their CRP, which is a measure of inflammation, went up.)

The take-away from this very good study is this: Stick with whole foods, minimally processed. “We should avoid severely restricting any major nutrient and focus on the quality of the nutrient”, said Ludwig.

“It’s time to reacquaint ourselves with minimally processed carbs. If you take three servings of refined carbohydrates and substitute one of fruit, one of beans and one of nuts, you could eliminate 50 percent of diet-related disease in the United States. These relatively modest changes can provide great benefit.”


And hopefully we can finally put to rest the outdated notion that “all calories are created equal”.