Part of the reason we went through so much trouble to show that unprocessed animal food is healthy is that unprocessed animal food is very high in protein. Protein is much more filling than fat or carbs,970 and unprocessed animal food has more protein than any other food group. Certain plants have a decent amount of protein, but gram for gram, any plant pales in comparison to steak.971
In one trial, obese subjects ate diets made up of either 12% protein or 25% protein, with most of the protein coming from dairy and meat. After six months, the 12% protein group lost an average of 11 pounds. The 25% protein group lost an average of 20 pounds, and had better triglyceride numbers.972
A 2012 meta-analysis of 24 controlled trials found that high-protein diets are superior to lower-protein diets for both weight loss and minimizing muscle loss during weight loss.973
In America, we tend to eat enough protein at lunch and dinner, but fall short at the breakfast table.974 The main culprit is white flour in the form of bagels, muffins, breakfast bars, pancakes, waffles, and cereal. These processed foods have little protein compared to, say, eggs. Eating more protein at breakfast helps people eat fewer calories throughout the day, especially at night.975
How Protein Causes Weight Loss
Food isn’t just about taking calories in. In order to break food down, process it, and absorb it, your body also has to expend calories. And more than you might think.
The thermic effect of food is a measure of how many calories it takes to digest a certain food. This number of calories depends on the food. For carbs and fat, the thermic effect is relatively low. It’s about 5-10% for carbs, and 0-3% for fat.976 For every 100 calories of fat or carbs you eat, it takes anywhere from 0 to 10 of those calories just to digest the food.
But the thermic effect of protein is a whopping 20% to 30%.977 For every 100 calories of protein you eat, it takes 20 to 30 of those calories just to break the protein down.
That’s a big chunk.
A 2015 metabolic ward study split people into two groups. One group ate a high-protein diet, and the other group ate a low-protein diet. Both groups ate the same number of calories. On average, people in the high-protein group burned over 130 more calories per day.978
Eating more protein helps minimize the metabolic slowdown that accompanies weight loss,979 and causes less preoccupation with food.980 High-protein diets are easier to sustain than other diets,981 and help people maintain weight loss.982
And you don’t have to make drastic changes to reap rewards. Increasing protein from 15% to just 18% of total calories reduced the amount of weight people regained after weight loss by 50% in one randomized trial.983
Protein is so important to weight loss that some researchers are starting to think the success of low-carb diets has more to do with their being high in protein than low in carbs.984
And it all comes back to satiety.
In the satiety study, the food with the most protein was ling fish. Out of 38 foods, it came in 2nd place. On average, the protein-rich food group was rated 66% more filling than white bread, and nearly twice as filling as bakery products.985
You may have heard that high-protein diets are bad for your kidneys. But that idea is completely based on people with pre-existing kidney disease—some of whom, admittedly, are probably better off avoiding high-protein diets.
But there is no convincing evidence whatsoever that high-protein diets cause any sort of kidney damage in people without preexisting kidney disease.986
It would be similar to arguing that, since exercise can be problematic for people with certain heart conditions, that exercise is bad for cardiovascular health in general.
Which is ridiculous, of course.
People who regularly eat high-protein diets have been found to have normal kidney function.987 So have athletes and bodybuilders who regularly eat very-high-protein diets.988
But forget science. If eating lots of protein caused kidney disease, there would be countless stories of athletes and bodybuilders—many of whom eat staggering amounts of protein for years on end—suffering kidney disease later in life.
But this simply isn’t the case. I’ve been around lots of athletes and bodybuilders and ex-athletes and ex-bodybuilders, and I’ve never even heard of a single case of kidney disease.
Even eating huge amounts of protein for years on end doesn’t seem to cause kidney problems.
High-protein diets are great for losing weight and keeping it off.
970. Paddon-Jones et al., “Protein, Weight Management, and Satiety,” American Journal of Clinical Nutrition 87, no.5 (2008): 1158S-1561S.
971. Self Nutrition Data. https://nutritiondata.self.com
972. Skov et al., “Randomized Trial on Protein vs Carbohydrate in Ad Libitum Fat Reduced Diet for Treatment of Obesity,” International Journal of Obesity 23 (1999): 528-36.
973. Wycherley et al., “Effects of Energy-Restricted High-Protein, Low-Fat Compared with Standard-Protein, Low-Fat Diets: A Meta-Analysis of Randomized Controlled Trials,” American Journal of Clinical Nutrition 96, no. 6 (2012): 1281-98.
974. Leidy et al., “The Role of Protein in Weight Loss and Maintenance,” American Journal of Clinical Nutrition 101, no. 6 (2015): 1320S-1329S.
978. Bray et al., “Effect of Protein Overfeeding on Energy Expenditure Measured in a Metabolic Chamber,” American Journal of Clinical Nutrition 101, no. 3 (2015): 496-505.
979. Wycherley et al., “Effects of Energy-Restricted High-Protein, Low-Fat Compared with Standard-Protein, Low-Fat Diets: A Meta-Analysis of Randomized Controlled Trials,” American Journal of Clinical Nutrition 96, no. 6 (2012): 1281-98.
980. Leidy et al., “The Effects of Consuming Frequent, Higher Protein Meals on Appetite and Satiety During Weight Loss in Overweight/Obese Men,” Obesity 19, no. 4 (2011): 818-24.
981. Due et al., “Effect of Normal-Fat Diets, Either Medium or High in Protein, on Body Weight in Overweight Subjects: A Randomized 1-Year Trial,” International Journal of Obesity and Related Metabolic Disorders 28, no. 10 (2004): 1283-90.
982. Westerterp-Plantenga et al., “High Protein Intake Sustains Weight Maintenance after Body Weight Loss in Humans,” International Journal of Obesity and Related Metabolic Disorders 28, no. 1 (2004): 57-64.
984. Soenen et al., “Relative High-Protein or ‘Low-Carb’ Energy-Restricted Diets for Body Weight Loss and Body Weight Maintenance?” Physiology & Behavior 107, no. 3 (2012): 374-80.
985. Holt et al., “A Satiety Index of Common Foods,” European Journal of Clinical Nutrition 49, no. 9 (1996): 675-690.
986. Martin et al., “Dietary Protein Intake and Renal Function,” Nutrition & Metabolism 2, no. 2 (2005): doi:10.1186/1743- 7075-2-25.
987. Blum et al., “Protein Intake and Kidney Function in Humans: Its Effect on ‘Normal Aging’,” Archives of Internal Medicine 149, no. 1 (1989): 211-212.
988. Poortmans, J., and Dellalieux, O., “Do Regular High Protein Diets Have Potential Health Risks on Kidney Function in Athletes?” International Journal of Sports Nutrition 10, no. 1 (2000): 28-38.