If you’re trying to lose weight – which will get you there faster – reducing calories and changing the quality of your diet or exercise? Of course, you should do both. Yet, it would be helpful to know what contribution each component adds to the equation. What does science say about this issue?
In a recent study, researchers reviewed 117 different studies (a meta-analysis) looking at the role diet and exercise play in weight and fat loss. What this study showed was both diet and exercise are important for losing weight. Yet making smarter dietary choices and watching portion sizes was linked with greater loss of body weight. On the other hand, exercise led to a greater loss of visceral fat.
What is visceral fat? It’s belly fat that lies deep in your pelvic cavity and wraps around internal organs, including the liver and pancreas. You’re probably most familiar with subcutaneous fat, the type you can pinch between your fingers. Subcutaneous fat may be what’s motivating you to lose weight but visceral fat is most important from a health standpoint because visceral fat is associated with chronic health problems, like type 2 diabetes, metabolic syndrome, and heart disease.
So, dieting impacts the number on the scale more than exercise but exercise attacks visceral fat, a type of fat that increases the risk of health problems. While losing weight and body fat may be your main motivation, zapping visceral fat is critical to your long-term health. Visceral fat is strongly linked with insulin resistance, a condition that places you at higher risk of health problems. So closely related are visceral fat and insulin resistance that a study published in Diabetes showed removing visceral fat prevents insulin resistance.
Unfortunately, visceral fat and insulin resistance both increase with age. We’ve almost come to accept the fact that waistlines grow wider with age, partially due to the accumulation of deep belly fat. Even worse is the fact that visceral fat secretes inflammatory hormones that partially fuel insulin resistance. Once insulin resistance sets in, it’s even harder to shed visceral body fat, being that insulin is a fat storage hormone. It’s a vicious cycle that’s hard to win – unless you exercise. Adding fuel to the metabolic fire of insulin resistance is the muscle loss that goes along with aging. Each decade after the age of 30, you lose between 3% and 5% of your muscle mass. In response, your metabolism slows. So, you’ve got a double whammy – increased body fat and decreased muscle tissue. No wonder our metabolisms slow and it’s so hard to take off body fat as we age!
Exercise and Body Composition
When you cut back on calories to lose weight, you lose a combination of body fat and muscle. When you glance at the scale, you might feel good about the number you see – but what about your body composition? According to one study, participants who ate 500 calories daily lost more muscle than those who ate 1,000 calories daily in an attempt to lose weight.
Of course, you should never drop your calorie intake this low. Doing so slows your metabolism, increases the risk of nutritional deficiency, and, as this study shows, leads to greater muscle loss. The benefit of exercise, particularly strength training, is it helps preserve lean body mass when you’re trying to lose weight. It’s no good when your weight loss turns out to be mainly muscle loss.
Maintenance of Weight Loss
Exercise also wins for weight loss maintenance. As you might know, losing body fat is only half the battle. Most people who lose more than 10% of their body weight gain it back. The reason? For one, your metabolism slows and your body is smaller, so you need fewer calories. Another factor: It’s easy to slip back into old eating habits. In addition, your body tries to return to its “set point,” the weight at which it feels the least threatened by starvation. Your body isn’t comfortable with changes, like losing a lot of weight. It tries to steer you back to your old weight by activating hunger, by becoming more efficient at using energy, and by, without your conscious awareness, causing you to move less. So, you’re fighting an ongoing battle to maintain the weight you lost.
Fortunately, research shows exercise is key to weight loss maintenance. As data from the National Weight Control Registry points out, people who lost at least 30 pounds of weight and kept it off for a year or more burn, on average, 2,800 calories weekly by exercising. They devote a portion of each day to working up a sweat. Animal studies also show that exercise is the key to successful weight loss maintenance. Another study showed that women who did an hour a day of moderate-intensity exercise were more successful at maintaining weight loss than those who were sedentary. It’s likely that high-intensity exercise for a shorter duration would be just as effective without spending an hour a day working out.
The Bottom Line
Yes, you can lose weight through calorie restriction alone but gaining it back is a real concern if you don’t exercise regularly. Plus, you won’t lose the same degree of visceral fat, the most dangerous kind, if you do it by diet alone. You’re also not improving your body composition since you’re losing muscle along with fat.
The best approach to successful weight loss and maintenance is to adopt a healthier diet consisting of REAL food, lots of plants, and exercising consistently, both aerobic and strength training. You don’t have to do long periods of cardio – try high-intensity interval training. HIIT training seems to be particularly effective for reducing belly fat and improving insulin sensitivity. So, don’t think in terms of “either,” or” but both! You need exercise and healthy eating habits to lose weight, improve your body composition and your health, and maintain it.
Obesity Reviews 17(8) · May 2016 “A systematic review and meta-analysis on the effects of exercise training versus hypocaloric diet: distinct effects on body weight and visceral adipose tissue: Effects of exercise versus diet on visceral fat”
Harvard Health Publications. “Abdominal fat and what to do about it”
Diabetes Care 2005 Sep; 28(9): 2322-2325. http://dx.doi.org/10.2337/diacare.28.9.2322.
Diabetes. 2002 Oct;51(10):2951-8.
WebMD. “Fast Weight Loss May Mean Muscle Loss”
University of Colorado Denver Newsroom. “Exercise Minimizes Weight Regain”
Obes Rev. 2005 Feb;6(1):67-85.
J Obes. 2011; 2011: 868305. Published online 2010 Nov 24. doi: 10.1155/2011/868305
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