Another study adds to the evidence that a high-protein diet is best for weight loss.



I’ve been promoting the health benefits of a high-protein diet for years. During that time, research and experience have only added evidence to the idea that a high-protein diet is ideal for weight management. 



A study published in The American Journal of Clinical Nutrition adds further evidence to protein’s impact on body fat. 





Research Study Design



Researchers compared the impact of consuming only protein-rich shakes multiple times each day to an equal-calorie, normal-protein, whole-food diet. They use the term high-protein total diet replacement (HP-TDR) to describe the protein-shake only protocol.



The total energy intake was the same between the two diets, but the high-protein diet group consumed 211 grams of protein per day, while the control group consumed 83 grams per day (about the same as the average American consumes each day).



High-ProteinControlEnergy, kcal/d2129 ± 2412128 ± 241Protein % energy39.9 ± 0.315.3 ± 0.3 g/d211 ± 283 ± 9Fat % energy24.9 ± 0.330.2 ± 0.3 g/d58 ± 672 ± 8Carbohydrate % energy35.2 ± 0.354.4 ± 0.4 g/d186 ± 21295 ± 34Sugars, g/d179 ± 214.6 ± 0.5Fiber, g/d4 ± 092 ± 12Saturated fat, g/d 12 ± 129 ± 3Monounsaturated fat, g/d35 ± 316 ± 2Polyunsaturated fat, g/d5 ± 031 ± 4Cholesterol, mg/d38 ± 917 ± 1



I have to point out a few things about the high-protein diet, outside of the protein, that a typical dietitian would say is bad. I do so only because when people focus only on components of nutrition such as sugar or fiber, they overlook the components of a diet that really make a difference.



As this study shows, a higher-protein intake has a significant, positive impact, in spite of other aspects a dietitian would say will make you fatter and sicker.



First, the difference in sugar intake. The high-protein group consumed 179 grams of sugar per day, 96% of their total carbohydrate intake. It’s also more than seven times what is recommended for daily sugar intake by public health advocates. Sugar is supposed to make you fat, right? Or a diabetic? We’ll see…



Second, the difference in fiber intake. Low-fiber intakes are also supposed to make you fat, aren't they? Well, the high-protein group consumed only 4 grams of fiber per day. Meanwhile, the control group consumed 92 grams of fiber per day.



When you speak to a typical nutritionist or dietitian, they’ll often speak of sugar as poison and fiber as a miracle food. Both points of view are highly exaggerated.



Third, the protein source was soy. I typically recommend avoiding soy protein. It has a lower bioavailability and contains soy isoflavones, which mimic estrogen. Would the results be different from an animal-based protein source? Perhaps, but based on other research, I'd expect a similar outcome. That said, the results in this study speak for themselves.



The study participants spent 32 hours in a whole-body calorimetry unit (WBCU), which is the most accurate and expensive way to track metabolic rate measures.



The following is a visual depiction of the study protocol:







Due to its expense and the difficulty in having someone live in a WBCU for days or weeks, this is a short-term diet study. It's possible the findings would change over time, but based on my experience with clients eating higher-protein diets, I highly doubt the results would change with a longer study duration.



Study Findings



According to the study authors:



The primary findings of this study were that compared with a standard North American dietary pattern, a HP-TDR led to higher total EE, increased fat oxidation, and negative fat balance (likely implying body fat loss).



Increased daily calorie expenditure, sleep, and post-meal metabolic rate



While individuals resting or basal metabolic rates did not change, they did burn more calories in total for the day, during their post-meal window, and even during sleep.