Low Carb or Low Fat for Weight Loss? cover

Low Carb or Low Fat for Weight Loss?

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Here we have a replay of the dueling diets thing, low carb vs. low fat. Low carb continues to appear to have a very slight edge, with many caveats. The sane advice continues to be that the best diet for weight control is the one you’re most likely to stick to. It’s easy to understand the craving for a conclusive answer. This rigamarole has gone on too long. There is certainly enough information now to at least make it clear that insisting on low fat as the only way to go is just plain wrong.
Low carb v. low fat for losing weight by by On Science Blogs, PLOS is licensed under a Creative Commons Attribution 4.0 International License.


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Low Carb or Low Fat for Weight Loss?

Those Dueling Diets

This week we have a replay of the dueling diets thing, low carb vs. low fat. Low carb continues to appear to have a very slight edge, with many caveats. The sane advice continues to be that the best diet for weight control is the one you’re most likely to stick to.

The paper that made the bigger splash came from the Annals of Internal Medicine (paywall) on Monday. The splash happened partly because it appeared to be the most careful comparative study yet. And it seemed to show that low carb was better, and that’s what the media said.

(Link here: http://annals.org/article.aspx?articleid=1900694)

Pork Roast Dinner

Pork Roast Dinner

Photo Courtesy: Warren Dew

(CC BY-SA 3.0)

Several Issues

That’s also what some bloggers I’d expect to be more careful with the data said. Shocking example: Incidental Economist Aaron Carroll.

His headline read: “Low carb crushes low fat. Screw you guys! I’m going home.”

Bottom line: After a year, the partly-Paleos lost 11.7 pounds on average and the low-fat folks a measly 4. Low carb was also better for cardio risk factors.

But not so fast. The study may have been the most careful yet, but that’s not much of a compliment. Obesity doc Yoni Freedhoff actually read the paper and pointed out several issues for the blog Weighty Matters (bit.ly/1qKTDyJ )

Self-Reporting

Food consumption tallies were based on self-reports. i.e., not reliable.

The low carb group lost 88% of their weight in the first 3 months. They were supposed to be eating no more than 40 grams of carbs/da but self-reported 80g during that time–and by the end said they were eating 112g.

Their self-reported calorie intake was lowest in the first 3 months too. It increased during the year, but by the end they were still taking in 100 cal/da fewer than the low-fat folks.

They did eat somewhat more protein than the low-fatties, and Freedhoff is one who thinks higher protein consumption may have more to do with low-carb diet success than reducing carbohydrates.

Women Only?

Both groups received diet counseling and a replacement meal bar or shake every day. Freedman thinks that controlled meal may have had a significant impact on the weight loss in both groups–which was in any case pretty modest.

He also concludes that the low carb diet was not truly that, nor was the low-fat diet (which specified 30% of calories from fat) truly low.

Kamal Patel makes some of these points and has some additional cautions at Examine.com. First, and maybe most important, 90% of the subjects were women.

Women

Women

CC0 Public Domain

Eat Less, Lose Weight

I’m not going to complain about including women in medical research. It took too many decades to get to NIH’s current policy

of insisting on a more rational sex ratio in clinical studies. But it does introduce the question of whether these results, unscintillating as they may be, apply to both sexes. There were 75 people in the low-carb group, and only 9 were men.

Patel concludes, “it would be disingenuous to state that ‘low carb is superior to low fat for long term weight loss’. . . A more accurate headline would have been: ‘If you are obese, decreasing carbs and upping protein may lead to greater weight loss, but sticking to any diet that has you eat less will lead to weight loss.’”

The Meta Analysis

The week’s second diet study appeared in JAMA on Wednesday behind a paywall. It was a meta analysis of several named diets,

for example the canonical low-carb Atkins and the equally canonical low-fat Ornish. The results showed low carb slightly ahead at 6 months but the two approaches were pretty much a wash at 12 months. Low fat and low carb, the paper said, turn out to be equally good.

Or, actually, bad. Average weight loss on either was between about 12 and 20 pounds. After a year.

These equivocal findings could explain why the JAMA paper hasn’t yet gotten anything like the reception of the earlier study, which was interpreted as proclaiming that low carb was superior.

Mediterranean Diet

Doc Howard LeWine examines both studies at the Harvard Health Blog and concludes that the Mediterranean Diet combines the virtues

of both approaches, although it doesn’t seem low carb to me. He’s part of the any-diet-that-you-can-stay-on-is-a-good-diet school.

It’s easy to understand the craving for a conclusive answer. This rigamarole has gone on too long. There is certainly enough information now to at least make it clear that insisting on low fat as the only way to go is just plain wrong - not only inaccurate, but maybe verging on morally wrong too. That includes various professional associations. Also the government.

Mediterranean Diet

Mediterranean Diet

Author: ADT 04

(CC BY 2.0)

USA

USA

Speaking of which, the Centers for Disease Control and Prevention has seized the moment and just published its depressing 2013 map of self-reported obesity state by state.