Last week we talked about metabolism and the three primary components that make up your metabolic rate. Let’s take a closer look at some the facts about improving your basal metabolic rate (BMR).
Basal Metabolic Rate is probably the most important as it is about 60% of your metabolic rate, so you get the most bang-for-your-buck by improving this. Let’s look at some interesting facts: A pound of muscle at rest needs 30-50 calories a day to survive, a pound of fat needs 5 calories. So a 175 pound person will need different calorie intake to maintain their weight depending on their body fat percentage. The more body fat compared to lean muscle the less calories needed to maintain your weight, which means you have to eat less the higher your body fat percentage gets even if you weigh the same.
Let’s look at where “yo-yo” diets can get you into trouble with this. Let’s take for example you lose 30# in one month when you go on a diet only to regain that weight back over the next year. When you lose weight you lose both fat and muscle weight. For this example let’s say you lost 20# of fat and 10# of muscle. When you gain the weight back it comes back in the form of fat, not fat and muscle unless you are doing strength training exercises. With the change in your body fat percentage going up with this example you will now have to eat about 300-500 less calories per day just to maintain your weight prior to going on this “yo-yo” diet even though you weigh exactly the same before and after. How much food is 300-500 calories? 2 pancakes, bowel of cereal, or a small plate of pasta less each day you can eat. While the equation and numbers in reality get a little more complex on how your body adjusts its metabolism, I want to point to the general picture – “yo-yo” diets mess with your metabolism in a bad way.
Many diets have you starving yourself, sometimes below your BMR. Simple thought is based on the formula: that if calorie intake is below metabolic rate you will lose weight. Which is true, but this is where the simple formula gets a little more complex. Your body and brain work together very closely to make sure you survive to the next few days. When they get signaling that starvation is happening over a few days it changes your metabolic rate to slow it down so that you won’t run out of energy to keep yourself alive until the famine passes and food is available again. It does this through slowing your BMR and taking energy stores from muscle instead of fat when it is needed. The body knows that it requires more energy to keep that muscle alive than fat, so the less muscle the better during a famine. So while this may seem like a good idea to lose weight you can see that it can quickly mess up your metabolism and not for the better. Faster weight loss will usually have increased muscle weight loss, where slower weight loss will usually be more fat weight loss. More fat weight loss means lower body fat percentage. That is why the fastest weight loss you would want is only 1-2 pounds or 1% of your body weight per week.
Next week we will get into the importance of activity, thermogenesis effects.
Kory Zimney is a practicing physical therapist in Iowa. He focuses on helping people move forward with their health and function through movement and exercise. This and other articles by Kory can be found at his blog: 
