Since we know how the body burns calories it would also make sense to understand what puts the breaks on our ability to burn calories. Or in other words what slows down our metabolism?
Now there are a number of factors that influence our metabolic rate. An older person burns fewer calories than a younger person, usually dropping by about 2% per decade. So if there were such a thing as copies of the same person in their 20s, 30s, 40s and 50s at the beach the oldest version at the beach would have a 6% slower metabolism than the version of themselves in their 20s. This is due simply to the fact they got older.
Now in combination with getting older and having a slower metabolism there is also the fact that testosterone drops as we age as well. From a peak in our twenties this hormone slowly declines starting in our thirties. With less of this anabolic in our body it is more difficult to build and maintain our lean body mass. As a result a smaller frame requires fewer calories to sustain it and our metabolism slows.
And besides our age and hormones there are other things which can disrupt our metabolism including prescription drugs, our sleep patterns, our overall health and our body type. With many of these we can’t do too much to influence our metabolism. For example, we can’t go back and choose better parents to alter our genetics. And it’s tough to stop time and prevent the aging process but some people do a pretty good job of staving off the effects of aging.
So knowing that there are some aspects of our metabolism that are completely out of our control means we have to be even more careful about the aspects which we can influence. For example consider when someone is dieting and trying to lose a few pounds. The typical approach would be to eat fewer calories, create a caloric deficit and hopefully drop some weight.
Here’s the problem.
As we reduce our caloric intake our metabolism slows. We eat fewer calories which lowers our thyroid hormone output, there is less thermic effect from feeding and we reduce our muscle mass. Don’t worry too much if you’re not familiar with thyroid hormone. For now if you understand that it is involved in our metabolism you’ll get the point.
So as we restrict calories we put the brakes on our metabolism. And this confuses a lot of people as they understand that weight loss requires a caloric deficit. And it does. However too much of a deficit and the body will think starvation is imminent and do what it can to slow down the ‘assembly line’ of calorie burning which is our metabolism.
I seem to recall from my Precision Nutrition certification course that our resting metabolic rate is most severely depressed when calories are reduced to the 1000-1200 calories per day range. So if someone required 1800 calories to maintain weight and reduced this to 1000 calories they may find that their metabolism slows, weight loss stops and it becomes more difficult to fuel their workouts without enough energy.
Guess what? The opposite is true of people looking to add lean mass. If the same individual that requires 1800 calories per day jumps their intake to 4000 calories they will see their metabolism spike. The body is overwhelmed with the overload of additional calories and ramps up metabolism in an effort to burn off the excess calories. Young skinny guys looking to add 10-20 pounds of muscle know this first hand.
So what’s the solution?
Whatever your goal make small changes and then track the results. By a small change I’m talking about a 10-20% difference in what your body requires for normal day to day activities where you maintain weight. Using the 1800 calorie example this might be 1440-1620 calories per day for weight loss. And for the person looking to gain mass this might be 1980-2160 calories per day. Monitor the changes in terms of your strength, energy levels, waist circumference, body-fat and mass then go from there making small adjustments every couple of weeks.