Are You Eating Enough? Low Calorie Diets and Metabolic Slowdown

By Lisa Rhea


Image courtesy of phasinphoto at

We have all heard it over and over again – weight loss is a matter of calories in and calories out. You have to eat less and exercise more. The more calories you burn, the more weight you will lose. The lower your calories, the smaller the number on the scale, right?

This is true, to a point. If you’re working out and/or watching what you eat and not losing weight, you may need to do less and not more. The problem could be you’re actually eating too little, exercising too much, or both.

The human body is incredibly adaptive. Much like jogging everyday will train the body to run more efficiently by strengthening the legs and better utilizing oxygen, eating at a deficit everyday teaches the body to use the food its getting more efficiently, to function on less calories – to burn less energy doing the same activities.

Look at many fitness competitors and bodybuilders who end up doing numerous hours of exercise a day on an extremely restrictive diet. Simple math would say an hour or two of cardio plus an hour of weight training should negate the paltry 1200 calories a day they’re eating. This should have them dropping several pounds a week, yet it takes them months to prepare for a competition. Why? Regardless of what their heart rate monitors tell them, their bodies have adapted and are holding on to every ounce of fat for dear life. Their metabolisms have slowed down to protect them from starvation.


Image courtesy of Mister GC at Eating less isn’t always the answer for weight loss.

Our body doesn’t understand that we want to look good in our bikinis or get that six pack in time for our birthday. It understands if it’s getting the food and nutrients it needs and time to recover from activity. And when it doesn’t get enough, regardless of your pant size, it will adapt in what it considers an effort to survive.

So how do you lose weight while maintaining a high functioning metabolism? The key is keeping calories high enough to avoid triggering the metabolic slow down. But before you run out and order a Big Mac and blame your lack of weight loss on too low of calories, let’s cover what too low really means.

In general, the best approach to weight loss is to cut the least amount of calories to effect change, thereby minimizing the metabolic response.

Everyone’s body adapts differently and will experience metabolic slowdown at different dietary levels. So how do you know if you’re calories are too low?

Here are a few signs that your metabolism isn’t functioning properly:

  • You’re not losing weight despite a strict diet and regular exercise. If you’ve been strict on your diet for weeks and don’t see results, it’s very likely that your calories are too low and your body triggered a hormonal shift to burn less and hold on to body fat.
  • You have trouble falling asleep or staying asleep. When you’re undereating, your body doesn’t have the glycogen stores to maintain your blood sugar, which leads to difficulty sleeping.
  • You’re constipated or not having regular bowel movements. If you’re not eating enough, you won’t be going much either. Besides just a volume issue, the thyroid also controls the activity in the gut, and if the body is in distress from too little nutrition, digestion will be sluggish and slowed.
  • You’re always cold. If you’re the only person cold all the time, or find yourself freezing in normal temperatures, it’s a good sign that your body is not generating enough heat, again a sign of metabolic slowdown.

Besides these obvious negatives of a slower metabolism, more reason to avoid under-eating or over-exercising is to avoid losing muscle mass and having post-diet rebound. When the diet stops or exercise ceases, the body will most likely return to its original weight. Yet, given the loss of muscle which occurred during the diet, often the metabolic rate will not be as high as it was prior to the dieting.

If you’re experiencing some or multiple signs of metabolic slowdown, you want to reconsider your current diet. If you’re not eating enough, start by slowly adding in more lean protein and healthy extras, like vegetables, fruits and good fats each day. Be prepared that it may take time to restore your metabolism and see weight loss results.

For more information on how to set up a weight loss nutrition, be sure to check out our Primer on Proper Nutrition and Breaking Bad: Dropping Weight Without Destroying Your Metabolism.

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