Check out the books in any bookstore and you’re sure to see several titles on how to boost your metabolism so you can burn away unwanted body fat. Many people are convinced that a “slow metabolism” is keeping them from losing weight. Each of us has a metabolic rate that’s determined by factors such as genetics, age and the amount of muscle tissue on our bodies. A 20-year-old muscle-bound male likely has a higher metabolic rate than a 60-year-old sedentary female who never picks up a weight. Health problems like an under-active thyroid and some medications can also cause a metabolic slowdown that makes it harder to lose weight.
Although age and genetics are factors that determine how fast our bodies burn energy, lifestyle factors do have an impact on metabolic rate. You’ve probably heard people say they’ve “damaged” their metabolism through aggressive dieting and find it almost impossible to lose weight as a result. Is there any truth to this idea?
In reality, metabolic damage isn’t permanent. Your body is a fine-tuned machine designed to maintain homeostasis at all costs. It adjusts its function based on the availability of energy supplies. Without these adjustments, humans couldn’t have survived periods when food supply was limited. Your metabolism too is capable of making adaptations, some of which work against you when you’re trying to lose weight.
Certain lifestyle practices can cause your metabolism to temporarily slow to conserve energy but this change isn’t permanent, although it may take time for things to return to normal. Ideally, you want to avoid doing things that cause your metabolism to slow down in the first place. Here are some to be aware of:
Dietary Factors
The most common dietary factor that causes a metabolic slowdown is excessive calorie restriction. In an overzealous attempt to lose weight quickly, some people drastically reduce their calorie intake to the point that their body senses starvation. As a rule, you shouldn’t reduce your calorie intake by more than 500 calories a day and should never go below 1200 calories daily even when you’re trying to lose weight.
When considering your calorie requirements you also have to consider the calories you’re burning through exercise and compensate. If you aggressively reduce your calorie intake, you may lose weight initially but inevitably your body adapts by holding onto whatever fat stores it can by slowing your metabolism. Just as importantly, you run the risk of losing lean body mass.
It’s not just a reduction in total calories that can slow your metabolism, eating a low-protein or very low-fat diet can too. A protein meal forces your body to work harder and expend more energy to digest and process it since it has a more complicated chemical structure compared to carbohydrates. Research shows diets higher in protein are effective for weight loss.
Another dietary practice that can slow your resting metabolic rate is fasting. Fasting is popular as a way to “detoxify” or “cleanse,” although fasting can also deprive your body of the nutrients it needs. Without adequate nutrition, the organs that “detoxify” like the liver, kidneys, intestinal tract, immune system can’t do their job as well. There’s no research showing fasting helps with detoxification, although fasting occasionally MAY have other health benefits. For one, intermittent fasting may improve insulin sensitivity and reduce oxidative damage to cells, based on preliminary research. In some species, animals that periodically fast live longer, although it’s not clear whether this also applies to humans. What is clear is that fasting temporarily slows your metabolism and could make it harder to lose weight. If you do it on a frequent basis, you run the risk of nutrient deficiencies and a more sustained metabolic slowdown.
Another form of fasting to avoid is skipping breakfast. After sleeping for 8 hours, your body needs fuel. Skimping on nutrition early in the day causes your body to conserve energy. A study published in the Journal of Epidemiology showed participants who ate less than 11% of their calories at breakfast gained almost 3 pounds over a 4-year period. Those who got 22 to 55% of their daily calories at breakfast gained only 1.7 pounds. Research has also linked eating breakfast with a lower risk of obesity. The take-home message? Start the day with a protein-rich breakfast like eggs to jumpstart your metabolism and stave off hunger.
Other Lifestyle Factors That Cause Your Metabolism to Slow
High-intensity exercise burns calories and creates an after-burn that temporarily increases your resting metabolic rate for hours after you finish. That’s a good thing when you’re trying to lose weight. On the other hand, doing extra-long or frequent moderate-intensity cardio sessions can have the opposite effect – it can slow your metabolism.
Not that you shouldn’t do steady state cardio, but pick up the intensity at least occasionally to increase the after-burn and reduce the duration of your workouts. It may seem counterintuitive, but the best bet is to focus on resistance training and short periods of intense cardio if you’re trying to lose weight. By building lean body mass, you’ll have more muscle tissue to burn energy during exercise and at rest. Your metabolism will have to speed up to meet the demand.
The Bottom Line?
When you’re trying to lose weight, be patient. Although your metabolism won’t be permanently damaged, it can take several months to repair your metabolism once you’ve damaged it.
Who wants that? Take the more conservative approach and the approach that’s better for your health.
References:
The Permanente Journal. Summer: 9(3): 16-18. (2005)
Women’s Health “Boost Your Metabolism”
Am. J. Epidemiol. (2003) 158 (1): 85-92. doi: 10.1093/aje/kwg117.
Today’s Dietitian Vol. 12 No. 2 P. 34. February 2010.
WebMD. “Is Fasting Healthy?”
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