by Marion Nestle
Sep 4 2014

The diet wars: same old, same old

To my great surprise, a new clinical trial finding that low-carbohydrate diets help people lose weight has been getting a lot of press. Its conclusion:

The low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet. Restricting carbohydrate may be an option for persons seeking to lose weight and reduce cardiovascular risk factors.

This is news?

The trial, conducted by authors who previously published a meta-analysis that came to the same conclusion, told people to eat either a low-carbohydrate diet of less than 40 grams a day (the amount of sugar in one 12-ounce soda) or a “low-fat” diet of 30% of calories from fat or less.

They didn’t do either, of course (for one critic’s analysis, see examine.com).

I put quotes around “low-fat” because 30% of calories is not exactly what I would call low—lower, for sure, but not low. After a year, the low-carb dieters lost about 3.5 kg more than did the “low-fat” dieters.  They also showed greater improvements in their risk factors for cardiovascular disease.

As I told Andy Bellatti

The folks eating the low carbohydrate diet…were eating less, and probably a lot less.  It’s easier for some people to lose weight if they cut out whole categories of food, in this case, carbohydrates.  But is this a long-term solution?  For that, we need to see results for several years.   Studies that examine the effects of different kinds of diets—and there have been many—typically find that all work to the extent that they cut calories, but that people have trouble sticking to extreme diets, which the low-carb one was in this study.  Personally, I like carbs and would rather cut my calories some other way, but that’s just me.  The bottom line: if you want to lose weight and are having trouble doing it, you need to eat less.

This profoundly boring conclusion, discussed at length in my book with Malden Nesheim, Why Calories Count: From Science to Politics, has just been confirmed by yet another meta-analysis.  This one doesn’t seem to be getting much press, however.

It reports significant weight loss with any low-carbohydrate or low-fat diet.

Weight loss differences between individual named diets were small. This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.

An accompanying editoria,  “A Diet by Any Other Name Is Still About Energy,” points out that study investigators only rarely analyze for how well participants in these studies actually adhere to the different diets, and for how long.

This makes it impossible for readers to figure out whether the weight loss was due to the specific components excluded from the diet or to the level of adherence.

In other words, whatever helps you eat less, helps you lose weight.  Go for it.

  • Med Jones

    Great writeup by Andy over at CivilEats.

    And thanks for the link to Examine.com – been digging into it for an hour, fantastic amount of detail.

  • A lot of people are on a low-carb diet today and in my opinion, it is healthier and more effective than a low-fat diet. It incites us to eat less calories by cutting high carb foods like sweets, bread, pasta etc. It also makes it easier to utilize the already consumed carbs, especially if we’re regularly training. Not to mention we get to experience other health benefits like lower LDL cholesterol, triglycerides, blood sugar and blood pressure. 🙂

  • Tom

    Why is Marion ignoring the finding that the low carb diet had greater effect on CVD indicators, it’s not always about weight loss. It bothers me when they classify diets as “low carb” when they aren’t. They are only low carb relative to the Western Diet of the last 50 years, thanks to grain processing by corporate food companies (there are a lot of fat vegetarians out there, that’s why they need to exercise so much). No culture in human history has ever consumed the amount of carbohydrates as this. What they don’t discuss, it’s what’s an easier diet to stay on with an equal number of calories – low fat or low carb?

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  • FrankG

    Indeed Marion… your critique of this news IS the same old same old thinking… 😛 “The folks eating the low carbohydrate diet…were eating less, and probably a lot less. It’s easier for some people to lose weight if they cut out whole categories of food, in this case, carbohydrates.”

    You say that it being easier to eat less naturally and without hunger this way, as if it is a bad thing somehow? Your reasoning against it is that IT WORKS?

    How is it that LOW carb means “cut out whole categories of food”

    Does LOW fat mean also “cut out whole categories of food” ???

    You are closed-minded and therefore doomed to provide poor advice to those who are dying to hear good advice.

  • Nate

    So, Marion, it is not news to you that a low carb diet is a better diet with which to lose weight and to improve your heart health. Having read your blog for about a year, I am very surprised to learn that you knew that.

    The bottom line is: Carbs with their sidekick gluten cause chronic inflammation and thus cause heart disease, diabetes, arthritis, dementia, cancer and other diseases of civilization. You may be able to chose to eat an extreme diet of less than 30% fat, but many people don’t have that choice if they don’t want to be obese. I still think you think that these people are gluttons and sloths and not people with difficult metabolisms.

  • Nate

    ‘The folks eating the low carbohydrate diet…were eating less, and probably a lot less.’ “Probably a lot less”, now, there is a scientific argument – probably.

    “It’s easier for some people to lose weight if they cut out whole categories of food, in this case, carbohydrates. But is this a long-term solution? ” Yes it is, as I’ve been doing it for 10 years now.

    “This makes it impossible for readers to figure out whether the weight loss was due to the specific components excluded from the diet or to the level of adherence.” What?? Who would what to know that? If reducing carbs helps you loss weight or/and helps you adhere to the weight loss diet, it still works.

  • Hi Mark,

    After three months of a low-carb diet my triglycerides went from 186 to 121, HDL from 42 to 48, and LDL from 150 to 199. Is this high LDL level cause for concern?
    Thanks Man!

  • Nate

    Hi Stomach Problems, Your high LDL level depends on whether or not the LDL is pattern A or B. The small dense LDL is the bad cholesterol and the larger fluffier is the good one. Your doctor can get you tested to see which pattern is greater.

  • Nate

    Hi Tom,

    I agree with your statement that “It bothers me when they classify diets as “low carb” when they aren’t. ”

    I think that some government agency from the US or EU or WHO should exactly define the terms “low fat”, “low carb”, “very low carb” etc. It would help relieve some of the confustion.

  • lisa

    Nate: You need some rest time.

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  • CynicalEng

    After 3 months there was no statistically significant difference in reported calorie intake between the two groups. Both continued to eat on average 500 cals less than baseline, and regained some weight from the 3 month low. That’s 9 months eating 25% less and not losing weight – bet that was fun.

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