By dotFIT experts
on September 29, 2008
As if the task of improving one’s health or fitness level isn’t challenging enough, fitness myths can cause confusion and frustration, and often result in wasted time. More...
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By Registered Dietitian
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By Registered Dietitian
on September 26, 2008
Years of misjudging your intake by just a few calories at a time will end up sabotaging your weight. For example, if you gain the average amount of one pound per year, this means you’re off by only 10 calories a day. More...

I've heard that when you eat fewer calories than you burn, the body perceives a threat (potential starvation?) and responds by slowing the metabolism. True?

I've heard that when you eat fewer calories than you burn, the body perceives a threat (potential starvation?) and responds by slowing the metabolism.  True?

Answer: There is no such thing as “starvation mode” or a significant slowing of metabolism for someone pursuing weight loss, even when they’re on a very low calorie diet. As long as you exercise while maintaining a calorie deficit and follow a healthy diet, you will always burn fat, allowing you to lose weight with maximum efficiency. When you come to a plateau you simply must move more, eat less or a combination of the two – period.

The myth
“Diet–induced slowing metabolism” is more of a myth than a problem. The myth was born from 1) reduced daily activities, resulting in fewer calories burned, meaning most people can’t eat much without gaining weight; 2) underreporting calorie intake -- people think they eat far less than they really do; and 3) sheer coincidence. By this we mean someone starts a new diet/exercise program thinking they increased their calorie intake, but in reality they are simply NOW following a plan that allows them to burn more calories than they consume. And this last point allows the myth to stay alive. If you are not losing fat/weight, it’s because you are not consuming fewer calories than you burn on average. Lastly, starving people do not stop losing weight or die fat.

More details
When you severely cut calories and lose weight, your metabolism may make a slight adjustment, allowing it to temporarily run on fewer calories. But it’s an insignificant (if it happens at all) for the typical dieter. A significant decrease in metabolic activity only happens in true starvation.  In other words, when someone IS starving, emaciated, AND still losing weight – NOT when you are overweight and at a plateau.

The main reason the body comes to plateaus during dieting or exercise (besides consciously or unconsciously not following the plan) is that you become more fit when weight is lost. Your body uses fewer calories to perform the same work, which forces you to have to perform more work or eat less in order to continue to progress. That’s not a slowing metabolism – that’s simply moving more efficiently with less weight throughout the day.

Another reason people think they are victims of a slowing of metabolism is that drastic diets may make them feel less energetic. This causes them to unconsciously move less throughout the day. Remember, we burn the vast majority of calories while performing daily activities, not during a one-hour workout. Also, a person may, through change in employment or other lifestyle alterations, simply start to move less throughout the day and now exercise cannot offset the decrease in daily calorie burn. And finally this: during very low calorie diets or at any time following significant weight loss, one often binges as the body attempts to recover lost pounds. And it only takes one “binge” to wipe out a week’s worth of accurate dieting. Most people can’t believe this because they worked hard to consume the proper amounts for seven or 10 straight days, so the one binge is either underestimated, forgotten, or they never grasped the fact that every calorie counts.

If you eat well, exercise regularly, and are experiencing a plateau, our general recommendation is to increase your daily movements at home or at the office. Never sit when you can stand or pace, such as when you’re using the phone. Standing burns two times and pacing uses almost three times as many calories as sitting! So get up and break your plateau. Additionally, changing your workout (including intensity and type of cardio you perform) can help burn a few more calories.

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