High dietary protein intake is associated with an increased body weight and total death risk, Clinical Nutrition, 7 April 2015

High dietary protein diets are widely used to manage overweight and obesity. However, there is a lack of consensus about their long-term efficacy and safety. Therefore, the aim of this study was to assess the effect of long-term high-protein consumption on body weight changes and death outcomes in subjects at high cardiovascular risk.

A secondary analysis of the PREDIMED trial was conducted.

Higher total protein intake, expressed as percentage of energy, was significantly associated with a greater risk of weight gain when protein replaced carbohydrates (HR: 1.90; 95%CI: 1.05, 3.46) but not when replaced fat (HR: 1.69; 95%CI: 0.94, 3.03).

Higher total protein intake was associated with a greater risk of all-cause death in both carbohydrate and fat substitution models (HR: 1.59; 95%CI: 1.08, 2.35; and HR: 1.66; 95%CI: 1.13, 2.43, respectively). A higher consumption of animal protein was associated with an increased risk of fatal and non-fatal outcomes when protein substituted carbohydrates or fat.

CONCLUSIONS: Higher dietary protein intake is associated with long-term increased risk of body weight gain and overall death in a Mediterranean population at high cardiovascular risk.

They found a 90% greater risk of gaining more than 10% of body weight over 5 years when protein replaced carbohydrate, a 59% greater risk of death when protein replaced carbs, and a 66% greater risk of death when protein replaced fat.

Note that animal protein was more harmful than plant protein.

I blogged about PREDIMED when it first came out. Recall that none of these people had heart disease before they started the study (7447 people “with no cardiovascular disease at enrollment”). It lasted just 4.8 years.

A high-protein diet is a diet high in animal food. It is very difficult to eat a lot of protein if most of your food is plant-based. Plant food contains protein but at a lower density than animal food. So, a plant-eater would have to eat a lot of food to get a lot of protein. As well, plant food contains fiber, animal food does not, so eating a lot of plant food will cause you to feel full sooner and may hamper consumption of a lot of food.

The study leader, Dr. Salas-Salvado, said, “Regarding the role of a high-protein diet in death risk, it could be due to increased kidney disease, changes in glucose and insulin metabolism, and also a modulatory role on blood fat profiles.”

But there’s something else, isn’t there. Those who eat a lot of animal food consume more hormone disruptors, and these chemicals have been shown to feminize men, to cause weight gain (are obesogenic), and are linked to a number of metabolic diseases, e.g. diabetes.