Why doesn’t food give me energy?

You supplied your height and weight details that give a reading of 20.5062 for your body mass index (BMI), which is a more accurate way of estimating body size. This, when looked up in tables, indicates either a chronic protein energy malnutrition (17-20) or the lower end of a “desirable” weight (20-25). I would suspect that you are, in fact, burning off your body fat. Your reduced energy levels would also indicate this.

It may well be that you do have a metabolic change that could involve your thyroid gland (over-activity) or even a sugar problem with a diabetic tendency. It is important, then, to obtain your doctor’s opinion, and you will certainly need a minimum of simple blood tests to try and determine possible problems.