Want to lose fat? Then, count your calories and burn off more than you consume. This mantra has been repeated so many times throughout the past several decades that this simple mathematical equation has spun off into numerous diet programs, meal plans, calorie-counting apps and even devices you wear that estimate how many calories you are burning. In fact, we have become so good at counting calories that many dieters don’t need an app since they’ve memorized the calorie content of hundreds of foods. Yet, something is missing from this “calories in, calories out” theory— a critical element that may mean the difference in yo-yo dieting or keeping weight off forever.
Though faithful devotees of high-protein or Paleo-like diets may turn their nose up in complete disgust at the thought of merely counting calories, one can’t argue with basic, though not entirely precise, math. If a healthy person consistently burns more calories than they consume, they will lose weight over time. In addition to research studies showing this principle is in fact true, some people have gone out on a limb to prove that total calories are what matters the most. In dramatic fashion, a professor at Kansas State University decided to experiment a few years ago. He ate fewer calories than he needed to maintain weight— 1,800 calories per day— in the form of Twinkies, Hostess desserts, Oreos and other less-than-nutritious snacks. He lost 27 pounds and what’s more amazing is that his diet of less-than-nutritious food led to improvements in his cholesterol and triglycerides— which goes to show just how important total calories are for weight loss and the importance of weight loss for changing blood lipids. But, this study doesn’t tell us the full picture.
Though taking in fewer total calories than you burn may be one key to weight loss, you can alter the type of weight you are losing, in favor of fat, by focusing on one macronutrient: protein. A study examined weight loss in 31 overweight or obese postmenopausal women prescribed a reduced-calorie diet. The women were placed on a 1,400-calorie per day diet (with 15%, 65% and 30% calories from protein, carbohydrate and fat respectively) and randomized to receive either 25 grams of maltodextrin (a carbohydrate) or whey protein supplement twice a day for the six-month study period. The group receiving the protein lost 3.9 percent more weight than the carbohydrate group, and they also preserved more lean body mass.
How Does Overeating Affect Weight Gain?
If protein is so important and helps preserve muscle mass, can you tip the scales in favor of a high-protein diet and preserve muscle mass while burning extra body fat and eat till your heart’s content? Probably not. A unique study led by George Bray, MD, examined how overfeeding affects weight gain. Bray’s research team recruited 25 healthy weight-stable adults, ages 19 to 30, and had them stay in an inpatient metabolic unit so they could control their food intake. For the first 13 to 25 days of their stay, the participants consumed a weight-maintenance diet (to help determine total daily calorie needs). After this period they were randomized to receive five percent, 15 percent or 25 percent of their total daily calories from protein and were overfed by 40 percent more calories than they needed every day to maintain their bodyweight. For the eight-week overfeeding period, the low-protein group ended up receiving six percent of their calories from protein (an average of 47 grams/day), 52 percent from fat and 42 percent from carbohydrate, while the normal protein group received 15 percent of calories from protein (139 grams/day), 44 percent from fat and 41 percent from carbohydrate. And finally, the high-protein group ate 26 percent of energy from protein (228 grams/day), 33 percent from fat and 41 percent from carbohydrate.
Though all groups gained weight, the low-protein (5%) group gained only 3.16 kilograms, whereas the normal (15%) and high-protein (25%) groups gained significantly more— 6.05 kilograms and 6.51 kilograms respectively. All groups gained a similar amount of fat mass with an average gain of 3.51 kilograms, indicating that overconsumption of calories alone accounted for the increase in body fat. And while the low-protein group gained less weight overall and gained a similar amount of fat as the normal and high-protein groups, 90 percent of the extra calories consumed on the low-protein diet were stored as fat, compared to 50 percent of the calories consumed on the normal and high-protein diets. In addition, the low-protein group didn’t gain any muscle and in fact lost 0.70 kilograms over the study period. The normal protein group and high-protein group gained more total weight because they packed on some muscle— 2.87 kilograms in the normal protein group and 3.18 kilograms in the high-protein group. Also, the normal and high-protein diet groups increased their resting energy expenditure, so they burned more calories at rest. This increase is likely the result of the body burning through calories to build muscle— a calorically expensive activity. The low-protein group experienced no change in resting energy expenditure.
The message from this study is clear— overeat, regardless of where those calories are coming from, and you will gain body fat. Increase your protein intake and you’ll experience a subsequent increase in muscle. And while this study labeled the group who consumed six percent of their calorie intake from protein a “low-protein” group, and their diets contained less than the recommended daily allowance for protein— an average of 0.68 grams per kilogram bodyweight (the RDA for adults is 0.8 grams per kilogram bodyweight)— their total daily protein intake, at an average of 47 grams per day, was only slightly less than what the CDC recommends for men (a mere 56 grams of protein per day; for women it is even less— 46 grams).
The results of this study also put an age-old theory to rest— that eating a diet low in protein or high in protein makes a person metabolically inefficient. You end up burning through calories to spare muscle on the low-protein diet and build it on the high-protein diet. As shown in this overfeeding study, you can’t fool your metabolism. If you overeat, regardless of whether you eat a low- or high-protein diet, you will gain fat.
Other Advantages of a High-Protein Diet
In addition to helping add muscle during weight gain, a higher protein diet (25% of total calories, for instance) will help spare muscle losses during weight loss and help prevent weight regain after weight loss. If you eat a protein-poor diet (or an inadequate amount of protein) while losing weight, you’ll lose some muscle tissue, your metabolically active tissue— the kind that helps you burn more calories at rest than fat tissue. And though the amount of calories your muscle burns while you are sitting and doing nothing isn’t really that much (add one pound of muscle and you may be able to chew an extra piece or two of sugar free gum during the day), the calorie difference adds up over time. And, the more muscle you have, the harder you can work out and therefore the more calories you can burn during your training sessions. Less muscle means less intense workouts and fewer calories burned.
Another take-home message— consider not just the numbers you see on the scale when you lose and gain weight but also changes in body composition. Oftentimes, physicians rely on body mass index— a measure calculated from one’s weight and height and used as a measure of body fatness. However, BMI was developed to look at population-based rates of obesity, not whether or not a single person is obese. BMI tells nothing about body composition— one can be over their recommended BMI but still carry an ideal body fat percentage. Or, conversely, a person can have a low or normal BMI but still be overfat.
If you aren’t losing weight, it’s time to take a look at both what you are eating and your total calorie intake. Be sure to consume enough protein, eat protein at every main meal (an even “distribution” of protein throughout the day is optimal for maintaining or building muscle) and stay within your recommended calorie intake. Doing all three of these things daily should result in weight loss and positive changes in body composition.
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Zhaoping L, Heber D. Overeating and overweight: extra calories increase fat mass while protein increases lean mass. JAMA 2012;307:86-87.
Bray GA, Smith SR, de Jong L, Xie H, Rood J, Martin CK, Most M, Brock C, Mancuso S, Redman LM. Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial. JAMA 2012;307:47-55.
Protein. CDC: http://www.cdc.gov/nutrition/everyone/basics/protein.html.
Mojtahedi MC, Thorpe MP, Karampinos DC, Johnson CL, Layman DK, Georgiadis JG, Evans EM. The effects of a higher protein intake during energy restriction on changes in body composition and physical function in older women. J Gerontol A Biol Med Sci 2011;66:1218-25.