Why The 500 Calorie Deficit Is a Lie
Raise your hand if you’ve heard the following: “Eat 500 calories less per day to lose a pound a week!” Common diet myths abound throughout the Internet. A simple internet search for “lose weight fast” will provide an endless array of supplements, caloric restrictions, and incorrect advice. At your local grocery store checkout line, you will find many magazine purporting the claim “Shed 10 Pounds in 1 Week!” While we don’t support any weight loss gimmick, it is important to refute incorrect information across the internet. Weight loss will happen on a deficit of calories, that much is true. However, the true picture of health extends far beyond that, to the types of foods you eat—such as nutrient rich whole foods versus processed junk food—to hormonal health to create a weight loss chart that is not linear.
So, Why is the 500 Calorie Deficit a Lie?
Let’s look at the research and begin to understand why simply reducing your calories by 500 each day will not result in weight loss.
One pound does not necessarily equal 3,500 calories
So, one oft touted piece of diet advice goes like this: Reduce your daily calories by 500 each day to lose a pound a week. Over seven days, you have reduced your calories by 3,500.
The 3,500 calorie per pound standardization comes from research done in 1958 by Max Wishnofsky and has been readily adopted and continues to be used today. For those of you that don’t want to read the full study, here is a quick synopsis:
One pound equals 454 grams
Pure fat contains 8.7–9.5 calories per gram
Body fat tissue is 87% fat
In 1899, a scientist named Wilbur Atwater, developed the caloric values for food that we still use today. Through his research using whole body calorimeters, the Atwater values, establish the values of the macronutrients as follows: carbohydrates (4 calories), protein (4 calories), and fat (9 calories). So, if you see 4g of fat on a nutrition label, it’s generally assumed that there are 36 calories from fat in that item. However, this specific mathematic equation only exists in a perfect vacuum, because it does not account for discrepancies of the digestibility of various foods, such as nuts.
The same can be said about the fat percentage in a pound of adipose, or body fat, tissue. Adipose tissue is loose connective tissue made up, primarily, of adipocytes. These cells store lipids for future energy use. Wishnofsky’s study found that the average body fat tissue is 87%. However, that number cannot be standardized across the body fat tissue of all individuals.
Even so, using the above values, one pound equals 454 grams. When multiplied by the 87% value of fat in each pound of tissue, we end up with approximately 395 grams of fat. This gets us somewhere between 3,436 calories to 3,752. Again, while 3,500 is an approximate value, it is not absolute.
The Body’s Response to Diet
Another topic that this myth fails to address is the body’s physiological response to changes in its composition and your diet. The 500 calorie deficit assumes that all weight loss is linear. When you eat less, your body responds in kind. Often incorrectly labeled “starvation mode,” this physiological resistance to sustained weight loss is known as ‘adaptive themogenesis.’ This study suggests that both men and women, respectively, experience a reduced daily energy expenditure (EE) relative to weight loss.
Furthermore, the findings from this study support the hypothesis that the body “resists” weight loss. In both obese and non-obese individuals, the autonomic nervous system (ANS) responded to weight loss in excess of 10% of initial body weight by increasing the amount of parasympathetic control (PC) and decreasing the amount of sympathetic control, through the changes in atropine and emolol, respectively.
Long term, massive weight loss can lead to loss of fat-free tissue and changes in resting metabolic rate. Through coordinated adaptive responses, the body “opposes” weight loss and results in the inability to maintain a reduced body weight. Subsequently, this predisposes individuals to regain the weight lost, unless exercise intensity and calorie are maintained.
The body’s Metabolic Response to Different Food
The 500-calorie deficit diet method also does not take into consideration the role that different types of foods play on energy expenditure. When you eat, a process known as the thermic effect of food occurs. Simply put, this is a caloric burn that occurs as your body digests and metabolizes your meal. This thermic effect is different for each of the macronutrients. The diet induced thermogenesis values are 0-3% for fats, 5-10% for carbohydrates, and 20-30% for proteins. The highest value for protein means that it has the highest energy expenditure during digestion. Protein also represents the highest value for satiety amongst all of the macronutrients.
This study also suggests that a higher thermic effect is seen when eating a meal comprising of whole foods in comparison to a meal composed primarily of processed foods. While this study cannot be applied broadly to all whole food meals—due to varying levels of fiber content, for instance—it is supportive of removing processed foods from a healthy diet.
The primary claim of many diets is to reduce fat loss while maintaining lean body mass. The rationale is that, as you lose fat, you gain muscle, which, at rest, burns more than fat. While this is true, very low calorie diets also result in the loss of lean body mass as well as fat loss. However, research by Claude Bouchard, Ph.D., suggests that muscle only burns six calories at rest, only four more calories than fat. However, muscle accounts for only 20-25% of your total resting metabolism. The remainder of resting metabolism is made up of brain function (20%), heart (15-20%), liver (15-20%), as well as kidneys, lungs, and bodily tissue. As we have no control over these bodily organs, the increase in any lean body mass (and thus, caloric burn increase), is largely negligible in long term weight loss.
So, now what?
Yes, it is true that being in a caloric deficit results in weight loss. But, only in the short term. Without lifestyle changes, the predisposition is to regain any lost weight. One size does not fit all and fad diets are often a quick way to lose weight, but not sustainable.