Exercise is a calorie burner and burning calories is the key to losing weight, right? So, you exercise long and hard, hoping the additional calorie burn will help you slim down. Unfortunately, the calorie in, calorie out model for weight loss has suffered some setbacks recently. When you hold it up to scrutiny, it’s not an ideal model. Many experts now believe that the composition of the calories you take in matters most. The calorie out end of the equation is tricky as well. Even if you burn 300 calories by doing an intense workout, you may unconsciously compensate for the calories you burned by moving less after your workout.
Exercise and Weight Loss
What impact DOES exercise have on weight loss? Researchers at Loyola Chicago Stritch School of Medicine looked at this issue. They asked a group of 1,900 people from the United States, South Africa, Jamaica, Ghana, and the Seychelles to wear activity tracking devices for one week. These devices were designed to monitor physical activity. At the beginning of the study and at the end, they measured each participant’s BMI, height, and body fat. They also continued to monitor these parameters after the study ended and one year and two years later.
What they found was the amount of time the participants exercised didn’t correlate well with body weight changes over time. Some of the participants who got the recommended amount of exercise, 150 minutes per week, experienced no change in body weight or actually gained weight, while others who failed to meet the exercise guidelines lost weight. The results were consistent independent of the nationality of the participants, whether they were American or from regions around South Africa.
Before assuming that exercise is an ineffective weight loss tool, keep in mind that the study only measured physical activity over a short period. Plus, they didn’t account for the types of exercise the participants did. Some forms of exercise are likely better for weight control than others. For example, high-intensity interval training is more effective than walking and strength training offers additional benefits you don’t get from purely aerobic exercise. For example, strength training builds metabolically active muscle and helps modestly boost metabolic rate over time. All forms of exercise aren’t equal for weight control.
Why Diet Matters
Despite this, exercise without focusing on diet isn’t the best approach to getting lean. Studies show we compensate for the extra calories we burn by eating more. Depending upon the type of exercise, a workout may stimulate your appetite, causing you to consciously or unconsciously increase your calorie intake. Exercise tends to suppress appetite while you’re doing it and shortly thereafter, but has the opposite effect later in the day – it stimulates appetite.
Then, there’s the psychological component – you exercised and you feel justified in eating more. Sound familiar? If you hadn’t done a workout when you woke up, you might have passed on that 550-calorie muffin at Starbucks but when you’ve just done an HIIT workout, you feel entitled to that baked good that’s deceptively high in calories Add a frou-frou coffee drink to that and you’ve taken in more calories than what you’ll burn off in two workouts.
All in all, this study makes an important point. What happens in the kitchen and at the table matters. A workout sets off a chain of adaptations within your body that ignites appetite hormones and alters hormones, like thyroid hormones, that regulate your metabolism. All of this happens beyond our awareness. Unless you monitor what goes in your mouth, you can easily wind up with a positive caloric balance despite doing a challenging workout. Even if calories aren’t the end-all for weight control, you’re likely make less healthy choices after an intense workout. That’s why they say abs are made in the kitchen. Nutrition and exercise are BOTH important for weight control and body composition.
The type of exercise you focus on matters as well. Think of strength training as an investment in your metabolism. Strength training builds muscle, which, in turn, boosts your resting metabolic rate. A study carried out by Harvard T.H. Chan School of Public Health found that men who weight trained 20 minutes daily were more protected against gains in belly fat than those who did a similar amount of moderate-intensity aerobic activity. By focusing on large muscle groups and doing mostly compound exercises, you’ll burn calories while increasing strength and building metabolically active muscle tissue. Strength training becomes even more important as you grow older as it reduces the loss of muscle mass, muscle strength, and functionality. Plus, if you use a heavy resistance, you also reduce the loss of bone mass as you age.
The Bottom Line
Exercise has numerous health benefits. In fact, exercise is the best natural medicine there is. However, it alone isn’t necessarily enough to lose weight or maintain your ideal body weight. So, think as much about what’s on your plate as you do your exercise routine. Exercise isn’t a license to eat whatever you want. On the other hand, diet by itself is disappointing for weight control as well. Dropping calories may lead to weight loss initially but your body will adapt and you’ll stop losing. Plus, the weight you lose will be a combination of fat AND muscle tissue.
Ultimately, you need exercise for a healthy body composition, especially as you age. Sarcopenia, the age-related loss of muscle tissue and strength, is at epidemic proportions in men and women sixty years of age and older. Losing weight without strength training places you at higher risk of this dangerous condition because you lose muscle as well as body fat.
The take-home message? Diet and exercise are BOTH important. Stick with whole, nutrient-dense foods and a combination of aerobic and strength training for weight control and better health. Pattern your diet after the Mediterranean eating plan, a diet supported by research. Studies show that this diet, rich in fruits, vegetables, nuts, whole grains, fish, and healthy fats, is linked with a lower risk of cardiovascular disease, type 2 diabetes, and some forms of cancer. Plus, it’s associated with reduced all-cause mortality. Although you shouldn’t be obsessed with calories, keep a food journal for a week and get a better idea of how much you’re eating after a workout. It could be enlightening.
Live Science. “Why Exercise is Not Enough to Prevent Weight Gain”
Harvard Gazette. “Using weights to target belly fat”
Canadian Journal of Applied Physiology, 30(4), 475-499. (2005)