My Health & Fitness column in the Aiken Standard this week is about the problem of losing weight on a diet then gaining it back soon after the diet ends. Many people who lose weight go back to their “normal” way of eating. The problem is that the “normal” diet of most people is hardly normal at all and is certainly not consistent with maintaining weight loss. In the article I give an example of a man who loses 50 pounds but goes back to the way he ate before losing that weight. After losing weight, his energy (calorie) needs are lower than they were when he was heavier. As a result, he was eating 500 more calories each day than he needed to maintain his new lower weight. Predictably, he gained the weight back even though he exercised every day. What he needs is a new “normal” diet.
The reason for this has to do with total energy expenditure (TEE), a measure of how many calories a person needs to maintain their weight. TEE is determined by two major components: Resting metabolic rate (RMR)–what most people refer to as their “metabolism”– and the energy expended in activity. RMR is based on body size and sex; the energy of activity is based on how active you are, including occupational activity, exercise, and other activity.
TEE is useful because it represents the number of calories you need to eat to maintain your current weight, assuming your activity doesn’t change. It is also a good way to come up with a calorie goal for a diet. For example, if your TEE is 2500 calories/day and your diet is 1,500 calories/day you are cutting out 1,000 calories/day. This should lead to a weight loss of 2 pounds per week. I also use this information to help explain why someone isn’t losing weight at quickly as they expect. The culprit is usually that they are eating more than they think they are, likely because portion sizes are too big. (If you have done this, don’t feel bad. Estimating portion sizes and calories is challenging, even for “experts”)
RMR can be measured in a lab, but it is usually estimated using a complicated formula based on age, height, weight, and sex. Energy of activity can be estimated based on your usual level of physical activity. You can calculate your own total energy expenditure using the following equation below, which is super-simple but accurate enough for most purposes. More complicated equations can be used for research, but that isn’t necessary here.
Step 1: Calculate your RMR
RMR (calories/day) = weight (kg) x 24
(note: weight in kg = weight in pounds ÷ 2.2)
Step 2: Calculate TEE
TEE (calories/day) = RMR x activity level
- Sedentary (mostly sitting with some light activity) = 1.4
- Active (daily physical activity at work or daily moderate exercise) = 1.6
- High active (heavy manual labor job or vigorous exercise) = 1.8