A widely known piece of diet advice is the 3,500-calorie-rule, which goes like this: If you decrease your intake by 500 calories a day, you will lose one pound per week. This is based on the fact that a pound of fat stores about 3,500 kilocalories (or calories).
Sounds simple, right? So why doesn’t it always work? Or why does it work for the first few pounds, but then the weight loss slows or you hit a plateau?
First, to follow this rule you would have to cut back an average of 500 calories each day from the range of calories your body needs for weight maintenance. If you have been gaining weight, eliminating 500 calories per day from your usual intake will not result in losing a pound per week. It might, however, produce a less-significant weight loss, keep your weight stable or slow down the rate at which you were gaining.
Secondly, following the rule requires calorie counting, and people tend to underestimate how many calories they actually consume. In some studies, calorie consumption is underestimated by 600 or more each day. The effect of this error can be compounded for those who exercise with the intent of “eating back” some or all of the calories they burn because people tend to overestimate the calories they expend.
But even for the most compliant and diligent calorie tracker, the rule still will not hold up long term. Your body weight and your body composition play a major role in metabolism. Your body composition is the percentages of fat, bone, water and muscle you have. As body weight decreases, body composition is likely to change, too, due to fat and/or muscle loss. The 3,500-calorie rule does not account for how these factors affect metabolism.
In other words, the calorie deficit you initially created will likely have a lesser and lesser impact as you lose weight, causing a decreased rate of weight loss — or the plateau. Cutting calories more to compensate for a slower metabolism is not an effective solution either. If you eat fewer and fewer calories to continue losing weight at the same rate, your metabolism will get slower and slower, making it harder and harder to keep losing.
What you can do
Stay active and be consistent with it. A balanced diet with regular exercise will prevent unfavorable changes in your body composition as you lose weight. A lower body weight still will require fewer calories to maintain, but preserving your muscle mass will prevent your metabolism from plummeting. According to the Centers for Disease Control and Prevention, “Evidence shows the only way to maintain weight loss is to be engaged in regular physical activity.” Remember the idea is not just to expend calories but also to maintain or build muscle. Exercising in an effort to purge calories is extremely ineffective for weight loss. Consistent daily physical activity however helps keep your metabolism revved up and offers benefits that far exceed weight loss alone.
Next, calorie tracking can be a good tool for awareness, but for most people it’s not useful long term. Instead of making calorie counting part of your lifestyle, make listening to your body part of your lifestyle. You’re not doing yourself a favor when you skip meals or when you ignore your hunger in an effort to cut calories. Instead, respect your physical hunger by fueling yourself with nourishing foods and stop eating when you are comfortably full. Choose nutritious, balanced options 80 to 90 percent of the time, and allow for occasional treats.
Finally, focus on the process rather than the outcome. You can take charge of your day-to-day life developing healthy habits, but you cannot control the outcome. Feel good about the changes you are making; don’t let the number on the scale make you feel like a failure. You are not a machine and weight loss cannot be reduced to a simple math equation.
Cindy Solis is a registered dietitian at Gundersen Health System. For more information about nutrition and healthy eating, call Gundersen Nutrition Therapy at 608-775-3447 or go to gundersenhealth.org/nutrition.