Counting Calories. Are all calories created equal? Two diets, same calories—but can one get better results? We explore new research on whether some calories make you fatter than others
New research shows that carbohydrates, fat and protein all act differently in our bodies, proving that calorie-counting is more complicated than simple addition. Here’s the latest information on how different foods affect calories in, calories out and the ultimate number you see on the scale.
Counting Calories isn’t as simple as the number you see on your food label. In scientific terms, 1 calorie is a kilocalorie (kcal), which is the amount of energy required to raise 1 gram of water 1 degree Celsius. According to that definition, all calories are equal, whether from fat, protein or carbs.
So is a calorie a calorie? Biochemically speaking, many experts say yes. But when you address the physiological and psychological effect of calories from different foods, the picture changes.
“Let’s take a pure food example to illustrate how this works,” says Anne-Marie Nocton, MS, MPH, RD. “If someone were to eat all of her daily caloric requirement as fried onion rings, would the body respond the same way as if all of the calories came from raw spinach? No, because caloric absorption is affected by the composition of the food itself and by the amount of energy it takes the body to process that food. In this example, the body doesn’t need to expend many calories to digest and store fat (in the onion rings) because the digestion and storage process isn’t very complex. But the spinach contains fiber, and the structure of a fibrous food means that some of the calories will be ‘lost’ because the body cannot break it all down.”
The simple act of eating raises your metabolism, and eating certain foods raises metabolism even more. The energy the body uses in the digestion process is called the thermic effect of food (TEF). “Protein has a higher TEF relative to carbohydrate and fat,” explains Rick Mattes, PhD, MPH, RD, professor of foods and nutrition at Purdue University (West Lafayette, Indiana). While the TEF of protein is about twice that of carbs or fat, the overall contribution of TEF to total calories is small. In a 1,500-calorie daily diet, boosting the protein content from 15% to 35% of calories results in an increased TEF of 21 kcal, or calories, per day–not really very significant.
Mattes, who recently spoke about calorie equality at the American Dietetic Association conference in Anaheim, California, explains that other factors–like the form of a food, appetite, metabolism and dietary compliance–also play roles when you compare calories from different foods.
Taking the perspective that calories are equal as chemically processed in the body, Mattes looks at the foods rather than just the calories. When comparing and counting calories, the delivery system matters, he reports. Are the calories in solid or liquid form? Researchers comparing apple juice, apples and apple soup found that the juice led to only a small decline in hunger, while apples and even apple soup were better at combating hunger.
In another study, subjects were given either 450 calories of soda or jellybeans, and researchers measured how much they ate later that day. After drinking soda, subjects ate the same amount of calories as usual. After eating jellybeans, however, subjects ate less food later on, so the jellybeans in fact substituted for other calories.
Eating jellybeans and then reducing the amount of food you subsequently eat is called dietary compensation. Mattes notes that solid foods have greater compensatory responses than fluids. “Fluids add to the diet rather than replacing other foods. This is called a weak compensatory response,” he continues. And soda isn’t the only problem drink–it’s fluid calories in general, whether from juice or even milk. In other words, be careful of liquid calories, which may add to your total calorie intake rather than substituting for other foods.
Compare 100 calories of bread with 100 calories of chicken and 100 calories of butter. Mattes explains that high-protein food is most filling (it has the highest satiety rating), while high-fat food is least filling. Thus, eating a higher-protein diet could theoretically help you feel fuller and stay satisfied longer.
While high-protein foods are valuable for their fullness factor, foods such as nuts that are rich in fat and protein have also garnered attention. Many studies have shown that nuts, though high in calories, have high dietary compensation and may even increase metabolism. Mattes illustrated one study that found subjects’ resting energy expenditure was 11% higher after nut consumption.
Researchers at the City of Hope Medical Center (Duarte, California) studied two groups of overweight people, both on medically supervised low-calorie liquid diets. One group added 3 ounces of almonds to their daily diet, while the other group added the same amount of calories from complex carbs like popcorn and Triscuit crackers. Both groups ate the same number of calories daily, about 1,000. During the 24-week study, the almond-eating group lost more weight even though they ate the same number of calories as the carb group. Same calories, different results.
In the counting calories battle of low-carb vs. low-fat diets, low-carb is holding its ground. “Despite the initial skepticism of many investigators, [several] recent studies found that high-protein and/or low-carbohydrate diets do yield greater weight loss after 3-6 months of treatment than do low-fat diets” (Buchholz and Schoeller, 2004).
But not all experts agree that carbohydrate limitation alone results in weight loss. One researcher commented that “lower-carbohydrate diets were associated with reduced calorie intake … weight loss was predicted by calorie intake, diet duration and baseline bodyweight, but not by carbohydrate content” (Bray, 2003). A calorie deficit is needed for weight loss, and low-carb diets work to reduce calories, pure and simple.
Take a plate of spaghetti and meat sauce from an average restaurant. Of the approximately 650 calories on the plate, about 350 calories come from the pasta and the rest comes mostly from fat in the meat sauce. In this example, choosing a high-carbohydrate (spaghetti only) or low-carbohydrate diet (meat sauce only) would cut caloric intake in half. Either extreme results in a lack of choices and a lack of taste, which probably explains the decrease in total calories consumed (Seshadri, 2004).
Nocton remarks that no matter how precise the study design, diet research can be affected by unknown factors. Though a 1,200-calorie diet may be prescribed, study participants may eat more or less than that amount–even if food is provided and food records are kept. The bottom line? Total calorie intake affects weight, but a lower-carbohydrate diet might result in fewer calories consumed. The downside is that long-term health effects of high-protein/low-carb diets aren’t known, and calcium loss may be a concern (Eisenstein 2002).
A diet may generate weight loss, but only if it’s palatable enough for people to follow for an extended period. That’s where personal preference comes in–eat a diet you can stick to. Mattes illustrated one study examining participation rates in a moderate-fat compared to a low-fat diet. The moderate-fat diet had much better compliance after 18 weeks.
Nocton’s good news is that “longer-term data tell us that the best diet for good health, weight loss and body composition is the one people perceive as the most boring: unprocessed; high in fiber and whole grains; loads of fruits and veggies; possibly low-fat and fat-free dairy; and rich in the right kind of fats, from fish, flax and some nuts and seeds.” And you won’t find a study anywhere to refute the benefits of this kind of sound, healthy diet.
Lose the Liquid Calories. Because liquid calories are not correctly compensated for in the diet, they may just add to your total calorie intake, rather than substituting for other calorie sources.
Go for Protein. Protein will help you feel fuller longer, so include a serving at each meal. That’s about 3 ounces of cooked chicken/meat/fish or a non-meat source such as an egg or a handful of nuts.
Diet Right. The best diet plan is one that you can stick to–ditch a diet that makes you miserable.
Calories Count. Many experts agree that low-carb diets work because they lower calories significantly. Look at the bigger picture of calories, along with total carbs. Remember that active women need those carbs to fuel fitness performance and maximize recovery.
Authors Details: Beth Saltz from http://www.muscleandfitness.com