Myth– Not eating enough will cause me not to burn fat or lose weight. Over the years this idea has been put forth, usually by companies trying to sell you something.

The truth is when we say not eating enough that’s exactly what it means. You’re not eating enough which means that your body will use its reserves and possibly some muscle tissue to maintain life. There’s no way around this. You can’t violate the law of physics which tell us that you need a certain number of calories per day to maintain your current body mass.

A calorie is not an object rather it’s a measure of heat. When you consume food it’s either converted into body mass, burned as energy or stored as body fat depending on your total intake versus your caloric expense over time.

Here is the truth. Your body does make some metabolic adjustment to starvation. When you consume less calories than you need for maintenance, your body perceives that you are in starvation and responds by slowing metabolism. However, it can only slow metabolism by about 10% at the most.
Here’s an example: Let’s say your body needs 2000 cal a day to maintain its current mass. It doesn’t matter whether you eat 1900 or 100 cal per day, your body will senses starvation mode because both values are under 2000 cal. If your body reacts by adjusting metabolism by 10% this means your body needs about 1850 cal a day now to maintain its current mass.

Continuing, let’s say that you’re actually on a 1000 cal per day diet. Your body needs 1850 cal, your eating 1000, so there’s an 850 cal difference. It takes 3500 cal to constitute 1 pound of fat loss. So, it would take you approximately 4 days to lose 1 pound of fat (4×850 equals about 3500 cal).

Diet myths generally originate from the same sources as literary myths do; meaning there is usually some basis in truth which is stretched or altered to fit a given situation or to sell a given product.