It is very distressing that even after best efforts, why some people are not able to loose or maintain required body weight. Let us come across the reasons why it is so difficult.

Excess stored fat should be converted back into calories when the body next requires more energy. This does not typically occur now days for 4 main reasons-

1. We consume available Carbohydrate calories before Fat calories, just as a hungry person consumes the most readily available source of food, the human body always consumes the most easily convertible source of energy. It is easy for the body to convert carbohydrate into energy quickly because of its simplest molecular structure. This is why we crave carbohydrates when we have not eaten for a while or immediately after performing strenuous exercise. In contrast, fat molecules are more complex and require additional energy and time to be converted into energy (or burned).
2. Our body tells us to look for more food before using stored reserves, when we need energy we experience hunger typically for more carbohydrates long before the body turns to its stores of excess fat. We also eat much faster, it typically takes 10-15 min. from the time we ingest food until our hunger becomes satisfied. When we take time between courses or bites to digest food, hunger becomes satisfied with only the amount of calories require. But when we eat quickly, we often think we are hungry and keep on eating even though we have already ingested more than enough calories. sometimes we take feeling of thirst to as hunger and instead to take water we strats eating.
3. Readily available food causes our metabolism to stabilize at the higher fat level, when one put an additional fat, their daily BMR for calories increases. Where their hunger used to be sated with 2500 cal/day, these people now require app. 3000cal/day in order not to feel hungry. As long as food is readily available and people listen to their stomach (hunger) regarding how much to eat, their increased amount of weight will remain static.
4. We are not biologically programmed for the type of food we take today, our food today is very different than food (was when our biological program for storing energy was developed) it contains more fat. Our ancestors were mostly a low-fat vegetarian diet. The fat was so rare and so useful that our taste buds evolved to crave it.

Today, unfortunately, this sensory craving has been exploited by our food suppliers.