This phrase again—AHHHH! It is true, but it is mainly false.
When your calorie intake is less than your body’s fuel requirements and your cell engines run out of glucose (a sugar) these cellular engines turn to protein or fat to keep running. When the cell’s engines use fat stores or protein stores you can start losing weight. BUT we hate depleting our bank savings account, and our bodies react the same. Your body will make changes to prevent loss of fat stores and muscles. (your fat cells are our body’s savings)
How each person’s body conserves stored energy reserves (fat) is affected by hundreds of various factors. (Genetics, epi-genetics, gut microbiome, hormones, sleep time, activity, muscle mass and many more some yet undiscovered.)
Bad News #1: Most human bodies respond to famine (decreased food intake) by decreasing metabolism, increasing muscle efficiency, increased fatigue, and increased hunger.
Bad News #2: The more refined carbohydrates and sugars in your diet the more the body must increase blood stream levels of insulin. Guess what-insulin builds more and more fat stores.
The “Calories In, Calories Out” concept is worth exploring in-depth. For more information and some good news, read Part 2 here.