Many of my clients have heard me arc up at "low calorie diets".  Here's why.

All calories are not created equal and a calorie does not give reference to the nutritional value of a food other than how much energy it "yields" in a laboratory, nor does it tell us how the body will use it. 

Just because two meals have the same amount of calories does not mean:

- They will fill you up equally

- They will satisfy you in the same way

- They will meet the same needs (nutrition, satiety or other)

- They are equally healthy

- They will be as effective at helping you lose or control your weight

- Or that they will be broken down, used or stored in the same way by the body.

The body deals with different foods differently, and an emphasis on nutrient dense (or high nutrient) (and probably "whole food") is more important than an emphasis on "low calorie", for health AND FOR WEIGHT LOSS.

A study done on two groups of people found that the people who ate more junk food, had lower nutrient levels in their blood despite eating more actual food and more calories than the other group.  So they had bigger appetites, ate more food and were less nourished than the group who ate healthier food (and were satisfied eating less).

Another study by Harvard confirmed that weight loss is not just about the amount of calories we consume but also about the type of food the calories come from:

"In a 2012 Harvard study published in the Journal of the American Medical Association, 21 over- weight and obese young adults tried three different test diets—a low-fat diet, a very low-carb/high-protein diet, and a low-glycemic index diet—for four weeks at a time.

Each diet consisted of the same number of calories but differed in their protein, fat, and carbohy- drate content. In the low-glycemic index diet, participants ate carbohydrates that are digested and broken down slowly and cause a gradual rise in blood sugar levels (e.g. low-processed foods such as fiber-rich whole grains, nuts, or beans).

The result? Researchers found that the low-glycemic index diet actually speeds up metabolism and helps burn calories, making you lose weight faster, suggesting that all calories are not equal.

According to to an author of the study, David Ludwig, M.D., a professor in nutrition at the Harvard School of Public Health, “from a metabolic perspective, all calories are not alike, [and] the quality of the calories going in affects the number of calories going out.”

In other words,"Low Calorie" on it's own is not where the "magic" is. "Low calorie diet" can be ambiguous and misleading.  Calorie restriction is an effective weight control method (and in fact can also increase longevity), when done in the context of good nutrition principles. Calorie restriction should not be done ignorantly or at the expense of good nutrition, or it can actually compromise health and sabotage weight loss.

Source: Healthy Solutions to Lose Weight and Keep It Off, http://www.health.harvard.edu/