Does Your Body Burn Muscle Before Fat?

Non-stop cardio and a crash diet could lead you to an energy crash.
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Cut the calories, add the cardio, but don't overlook your muscles when planning a weight loss program. Sharply reduced food intake and increased aerobic exercise can have a negative effect on the lean muscles that make it easier for you to lose weight and keep it off. You could end up flabbier than fit if the pounds you lose are muscle instead of fat.

Diet Myths

Popular wisdom makes for ineffective weight loss strategies. Typically, a diet restricts calories and increases aerobic activity to peel off pounds. The more severe the diet and the more vigorous the workouts, the faster you reach your weight goals. But more cardio plus fewer calories can produce unintended consequences. The National Council on Strength & Fitness says that approach may negatively affect your body composition. Clinical trials show that reducing calories while adding aerobic training reduces fat but does nothing to preserve muscle tissue and can result in significant muscle loss.

High-Performance Fuel Mix

As you start to exercise, your body uses glycogen, stored in the liver and muscles, for fuel. The University of Michigan Medical School says that, after about 30 minutes, you switch to burning fat stores for energy. A long moderate aerobic session lightens your fat load and brings you a few steps closer to those skinny jeans. But if the exercise is high-intensity or you are not consuming enough calories, your body will convert protein from muscle fiber into energy. Instead of burning fat, you devour muscle tissue. Which fuel your body burns first -- muscle or fat -- depends on the way you structure your weight loss or fitness plan.

Cardio and Catabolism

Too much cardiovascular exercise depletes muscle mass and strength. If your calorie intake is too low and your aerobic training is too tough, your body will produce the catabolic hormone cortisol, which breaks down muscle tissue. Anita Bean reports in The Complete Guide to Strength Training that, when you are working out hard and eating less, your body is working just as hard to find the fuel for all that energy expenditure. Metabolism consumes fat and protein -- and the protein comes from muscle fiber. Trigger protein consumption and you cannibalize your muscles to fuel your fat-burning, a self-defeating maneuver. The Mayo Clinic points out that muscle tissue burns more calories than fat tissue so, as you work off excess inches, preserving muscle improves your odds of weight loss success.

Embrace Resistance

Resistance training can offset the negative impact of calorie restriction and cardio exercises on muscle mass and strength. Resistance training increases muscle size, boosts your resting metabolic rate and results in faster fat burning. According to the the National Council on Strength & Fitness, greater muscle mass elevates metabolic levels even when you are resting. Each extra pound of muscle equals an extra pound of fat lost per year while you sleep, not a bad way to stay fit. More muscle has additional important health implications. An absence of resistance exercise leads to lower muscle mass and lower bone density, a precondition for osteoporosis. Protecting your muscles while dieting could have long-term implications for mobility and independence, and your ability to maintain a healthy, moderate weight as you age.

Balanced Approach

A trifecta for healthy weight loss balances regular aerobic exercise, strength training and a nutritious diet containing sufficient protein. Moderate cardiovascular exercise builds muscle, according to Columbia University Health Service, which warns against extreme aerobic sessions that deplete glycogen and consume muscle. Opt for low to moderate aerobics and resistance workouts and be vigilant about diet. To preserve muscle mass, avoid fatigue and stimulate metabolism while dieting, eat five to six small meals throughout the day and include adequate protein. Harvard School of Public Health recommends fish, poultry, nuts and beans as protein sources that have very low amounts of saturated fat. Create a healthy mix of sound nutrition, cardiovascular exercise and resistance training to reach and maintain your ideal weight.

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