Food Safety

Nutritional Pearls: Is a Long-Term High Protein Diet Bad for You?

Jeffrey is a 63-year-old overweight man at risk for heart disease. Recently, in an effort to lose weight, Jeffrey shifted to a high-protein, low-carb diet. He is curious if this change will help him to not only lose weight, but improve his cardiovascular risk as well.

How do you advise your patient?
(Answer and discussion on next page)


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Answer: Research doesn't support that a high-protein diet is a good tool for managing weight in the long term.

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 long-term health. For these reasons, I don't hide the fact that I consider fad diets like the Atkins Diet, South Beach Diet, or the Paleo Diet to be silly. Not only is the quality of the science they are based on poor, but also the fact is that for most people, these are not diets they can live with for their entire lives.

High-protein diets like the 3 I mentioned above have been touted as helpful to people trying to lose more weight, lose it faster, keep it off, and even improve clinical scores like cholesterol and blood pressure more 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).1,2

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The Research

In today's study, 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 that I’ve reported on in the past. I've previously described the study thus:

"… [O]ver 8000 men and women between 55 and 80 who were considered to be at high risk for cardiovascular disease were randomly assigned to 1 of 3 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 underwent blood tests and body measurements on a yearly basis. For this study, the authors analyzed each participant’s 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 his or her waist circumference may have changed.

The Results

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 vs 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 showed a lower risk of death from cancer.

What’s the “Take-Home”?

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, linked to an increased risk of cancer, heart disease, and death from all causes. Bear in mind that two-thirds 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.


1. Bazzano LA, Hu T, Reynolds K, et al. Effects of low-carbohydrate and low-fat diets: a randomized trial. Ann Intern Med. 2014;161(5):309-318.
2. Halton TL, Willett WC, Liu S, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med. 2006;355(19):1991-2002.
3. Hernández-Alonso P, Salas-Salvadó J, Canela-Ruiz M, et al. High dietary protein intake is associated with an increased body weight and total death risk [published online April 7, 2016]. Clin Nutr. doi: