Susan M. Kleiner, Maggie Greenwood-Robinson
The old-fashioned way of figuring out how many calories you should eat to lose weight is to just chop off 500 to 1,000 calories from your current diet. One pound (.5 kilogram) of fat is equivalent to 3,500 calories. According to the laws of thermodynamics, if you feed yourself 500 calories fewer than you need each day for seven days, theoretically you should lose 1 pound (.5 kilogram) at the end of the week. Double that amount and you should lose 2 pounds (1 kilogram). But dietitians have known for years that it never works this way, and this strategy becomes more frustrating as the weeks of dieting wear on.
At Georgia State University, Dr. Dan Benardot wondered why these seemingly clear laws of physics don’t hold true within the human body. His research has shown that once food enters the biological system of the body, there are more variables at work than the simple number of calories that are given off by a pound of fat when measured directly in a science lab. The human body is a living organism, and the drive for survival allows the rules of the system to change based on thousands of years of adaptation to the environment. Dr. Benardot tested two groups of female gymnasts and runners: One group ate a diet of 500 fewer calories than they needed to maintain their weight each day, and the other group ate 300 fewer calories. What he found was astounding: The group that ate 300 fewer calories had a lower percentage of body fat than the group that actually ate less food. His theory is that when too few calories are eaten, resting energy expenditure (REE) slows down to meet the energy available to the body.
The ability of the body to slow metabolic rate to meet available energy has long been understood by scientists. Called starvation adaptation, it is induced in extreme circumstances of famine to allow the body to survive far longer than would be predicted based on normal metabolic rates of energy use. Dr. Benardot is proposing for the first time that even under mild states of energy deficit, energy use slows down. There is no benefit to eating far fewer calories than your body needs. In fact, he calls a 300-calorie deficit the ideal metabolic window for women to lose the most amount of fat in the shortest amount of time.
So forget low-calorie dieting. When you reduce your caloric intake by 300 calories (women) or 400 calories (men), you can keep your metabolic rate high enough to continue to burn fat at a good clip. Additionally, you want to have enough energy to perform at peak levels both physically and mentally. Here’s how to eat to give yourself the best chance at losing fat and saving muscle.
- Don’t starve yourself. Because you strength train and probably do aerobics as well, you actually need more food, not less. Researchers at Tufts University found that when older men and women began a strength-training program, they needed 15 percent more calories just to maintain their body weight. This finding is not so surprising, really. With strength training, the exercisers began to expend more calories. Plus, their RMR increased because they had built more muscle.
You can figure out exactly how many calories you need to lose fat. Based on my research with competitive bodybuilders, I have concluded that an intake of 35 to 38 calories per kilogram of body weight a day is reasonable for fat loss and muscle preservation. The minimum is 29 to 32 calories per kilogram for a rapid cut. Anything less than that is too restrictive, and you won’t be well nourished. Let’s say you weigh 180 pounds (82 kilograms). Here’s how to figure your calorie requirements to lose fat: 82 kg X 35 calories / kg = 2,870 calories. For maintaining body weight, you should eat up to 44 calories per kilogram of body weight a day, or 3,608 calories a day. If you want to build muscle and you increase your exercise intensity, duration, or frequency, go even higher—to 54 calories per kilogram of body weight, or 4,428 calories a day.
If you still need a calorie deficit to continue losing fat or to break a plateau, get that deficit by increasing your activity level and modifying your calories slightly. For example, restrict your calories by about 300 to 400 calories a day and increase your aerobic exercise. This deficit, again, is the ideal metabolic window for weight loss.
- Correct your dietary fat. Be sure to include the right kinds of fat in your diet, including omega-3 fats from fish and monounsaturated fat from olive oil, avocadoes, nuts and seeds, and nut and seed oils. A recent Australian study showed that when premenopausal women ate diets rich in monounsaturated fat, the diet helped them preserve muscle while losing weight. Diets high in omega-3 fats may actually protect against obesity; many studies have observed the fatburning effect of omega-3 fats. Include up to five fish meals in your diet each week. The more muscle you maintain while losing fat, the greater your chance of keeping the weight off for good.
- Preserve muscle with protein. To lose mostly fat and keep your metabolism running in high gear with muscle mass preserved, you must have adequate protein in your diet. Protein also helps control your appetite. If you go on a diet that is too low in calories, there is a good chance that your dietary protein will not be used to build tissue but instead will be broken down and used for energy much like carbohydrate and fat are. As a reminder, for losing body fat the nutrient profile of your diet should be 30 percent protein, 40 percent carbohydrate, and 30 percent fat.
- Concentrate on the right kinds of carbohydrate. These include high-fiber foods and foods with a low-glycemic load (see chapter 3), which promote fat loss. Regardless of what you hear or read, the right kinds of carbohydrate are critical to fat loss for reasons that bear repeating. First, carbohydrate is required in the cellular reactions involved in burning fat. Second, it spares protein from being used as fuel. Third, carbohydrate restocks the body with glycogen, which helps power the muscles during exercise. Fourth, when your body is digesting carbohydrate, your metabolic rate goes higher than it does when metabolizing fat. Finally, complex carbohydrate is loaded with fiber, which has its own set of fat-burning benefits.
If you are strength training and doing aerobics as part of your fat-loss program, you need to eat 4 to 5 grams of carbohydrate per kilogram of body weight daily for men and 3 grams per kilogram of body weight daily for women. This amount will keep you well fueled for high-intensity exercise while still allowing enough room for your extra protein needs.
- Monitor added sugar in your diet. Added sugar in your diet promotes fat gain by reducing the sensitivity of your cells to insulin so that insulin cannot shuttle sugar into your muscle. It then heads to the liver, which turns the sugar into fat. When you eat low glycemic-load foods, you avoid this situation entirely.
Case in point: Researchers at Indiana University in Bloomington, Indiana, analyzed the diets of four groups of people: lean men (average body fat of 15 percent), lean women (average body fat of 20 percent), obese men (average body fat of 25 percent), and obese women (average body fat of 35 percent). The obese men and women ate more of their calories from fat (as high as 36 percent of total calories) and refined sugars, such as candy, doughnuts, and ice cream, which are also high in fat, than the lean men and women. In other words, there was a link between high-fat, high-sugar diets and obesity.
The lesson is this: Change the composition of your diet to keep the fat off. This means cutting down on high-fat, sugary foods. If you have a sweet tooth, choose dark chocolate or combine the sweet food with a protein and a healthy fat so that you slowly absorb the food and slowly release sugar and, ultimately, insulin into your bloodstream. Stay away from beverages and foods sweetened with highfructose corn syrup, which has been linked to the incidence of obesity.
You may have thought about using artificially sweetened foods, but proceed with caution. See the section on artificial sweeteners on page 90 for more on the controversy over their use.
- Don’t skip breakfast. Skipping breakfast is not a good way to lose body fat; in
fact, it could even make you fatter! Most people who skip breakfast make up
those calories, with interest, throughout the day. In Madrid, Spain, researchers
found that overweight and obese people spent less time eating breakfast and ate
smaller quantities and less varied types of food at breakfast compared with
normal-weight people. Eating breakfast stokes your metabolic fires for the day.
By contrast, going hungry in the morning is just another form of fasting, which
slows down your metabolism. Plus, your physical and mental performance will
suffer when you are running on empty.
If you’re like me, you’re rushed in the morning, with barely enough time to shower and dress, let alone eat breakfast. If that is the case, eat what you can. Something is better than nothing. A study done in England found that because ready-to-eat cereals are high in vitamins and minerals and low in fat, they make a great choice for breakfast. When choosing cereals, whole grains, low sugar, and high fiber are the best bets. The best breakfasts include a combination of carbohydrate, protein, and fat. If you are always on the go, you need some nutritious breakfasts that take minutes to fix. There are several breakfast recipes in chapter 16 to help you. Some of these can even go on the road with you—so there is no excuse to skip breakfast!