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Yes, fad diets work, but....
One of the concerns with diets that drastically restrict the amount of fat, protein, or carbohydrates is the lack of evidence regarding their long-term effects on one's health, especially cholesterol scores. Researchers at Stanford University recently released a study comparing the effects of several popular diets (Atkins, the Zone, and Ornish) with the more traditionally recommended diet pattern of low-fat, high-carbohydrate, and reduced calories (JAMA 2007;297(9):969-977).

Low-Carb Diets Linked with Higher Risk of Type 2 Diabetes
If you've been following Dr. Gourmet for a while, you already know what I think about the Atkins Diet and other low-carbohydrate diets: why follow a diet - any diet - that takes entire food groups away from you? Certainly we know that such diets work to help people lose weight, which is largely due to the fact that when most people stop eating carbohydrates, they stop eating junk.


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Long term high protein diets: bad for you?

a hamburger made with beef and garnished with tomato, lettuce, and ketchup

I'm a practicing physician: I see patients every day. When I counsel my patients about their diet, I want to meet them where they are, in the world they live in, with the real challenges they face. I'm not interested in what might be a "perfect" diet: I'm interested in helping my patients make realistic dietary changes that they can live with for the long term for the sake of their, yes, long term health. So I don't hide the fact that I think that fad diets like the Atkins Diet, South Beach Diet, or the Paleo Diet are just silly. Not only is the quality of the science they are (supposedly) based on pretty poor, the fact is that for most people these are not diets they can live with for their entire lives.

High protein diets like the three I mentioned above have been touted as helping people lose more weight, lose it faster, keep it off, and even improve clinical scores like cholesterol and blood pressure better than either low-fat or high-carb diets. While some (poor quality) research has been interpreted to mean that a low-carb diet is better for you than a low-fat diet, other research has shown that over the longer term those following a low-carb diet were no more likely to develop heart disease than those following a higher-carb diet (although those consuming more vegetable protein did have reduced risk).

In today's study, published in a recent issue of Clinical Nutrition (2016;35:496-506), the authors used data gathered through the PREDIMED study (PREvencion con DIeta MEDiterranea, Spanish for "Prevention with a Mediterranean Diet"), a long-term, large scale study we're reported on before (here, here, here, here, and here). I've previously described the study thus:

...[O]ver 8,000 men and women between 55 and 80 who were considered to be at high risk for cardiovascular disease were randomly assigned to one of three diets: a Mediterranean Diet supplemented with a daily allotment of olive oil, a Mediterranean Diet supplemented with a daily allotment of mixed nuts (walnuts, hazelnuts, and almonds), or a low-fat diet (the control diet).

The study lasted about 6 years, and the participants filled out a detailed dietary questionnaire and submitted to blood tests and body measurements on a yearly basis. For this study the authors analyzed each participants' protein intake, classifying it as either animal or vegetable protein, stratifying the amounts (both total protein and whether animal or vegetable) by increasing amounts, and also classifying the individual's protein intake by percentage of overall daily calories as well as the average number of grams of protein per kilogram of body weight consumed per day. They also looked at whether an individual's body weight changed significantly and whether their waist circumference may have changed.

The protein intake of those who died over the course of the study was then compared with that of those who did not. Those who consumed the most protein (whether animal or vegetable) as a percentage of their total caloric intake were over 2 times as likely to die of heart-disease-related causes than those whose protein consumption was the smallest percentage of their total calories. Similarly, those with the highest percentage of calories from protein were as much as 48% more likely to die of cancer, and their total overall risk of dying from any cause was increased by 66%. Those who consumed the most protein were also more likely to gain weight, and those who consumed the highest percentage of calories in protein tended to have the highest Body Mass Index and body weight.

Interestingly, when the authors looked at vegetable protein versus animal protein, they "failed to find that vegetable protein was related to lower risk" of death from all causes, although a lower ratio of animal to vegetable protein (less animal, more vegetable) showed a lower risk of death from cancer.

What this means for you

These results just don't support people's belief that a high-protein diet is a good tool for managing one's weight in the long term. Further, a high-protein diet may be said to be bad for you, increasing your risk of cancer, heart disease, and death from all causes. Bear in mind that 2/3 of the people in this study were already following a Mediterranean-style diet: these results from higher protein consumption are in spite of the participants' overall dietary pattern. Moderation is still key.


First posted: April 27, 2016