The human body is remarkable at conserving energy. It will quickly adapt to changes in the external environment to create an internal state that it can maintain. You can increase the amount of daily calories you consume and your body will respond by increasing its metabolic rate to burn off the increase. Talk to any body builder and they will tell you that adding 3 pounds of muscle per month requires that you increase your caloric consumption by more than 350 per day; many lifters find that they need to eat an extra 1000-1500 calories per day to add any weight. If the body did not have the ability to adapt and boost metabolic functioning in response to caloric increases they would need just the 350 per day to add 3 pounds per month.
One of the more effective survival mechanism of the body is the fat storage system because it allows humans to store energy during times of food surplus and utilize that stored energy during food shortages. This system is, for the most part, an all or nothing thing – you will either be storing fat or you will be using fat.
Maintaining stored fat requires energy because body fat needs oxygen and, therefore, a blood supply. The cost is small, but over a long period of time, or if there is a lot of body fat, the cost will be dramatically increased. High blood pressure is one consequence to obesity because of the increased need for blood vessels to service the large amount of fat – the heart has to push blood around miles of extra tubing so it has to work harder.
However, the body does rely on what I can transient fat storage / utilization (TFS/U) to help it get through the periods of time when blood sugar level drops to a critical level and food is not eaten. TFS/U deals with periods of less than 12 hours, the usual maximum time that anyone will go without food as a result of sleep. Even people who eat a calorie balanced diet (equal in the amount of energy that they eat vs. what they burn off) will rely on the TFS/U throughout the day because they are eating three meals a day; this feeding schedule is insufficient at delivering the constant energy needs to fuel their daily activity. As a consequence, the body remains motivated to keep storing fat because it is being utilized fairly consistently.
The notion I am putting forward is that, in a caloric equilibrium state, the body will rid itself of excess body fat if we eliminate the need for transient fat storage. The rational is that the body will do what it can to conserve energy. Since body fat requires energy to maintain, energy can be conserved by getting rid of it. However, the only way to eliminate the need for TFS/U is to maintain a constant blood sugar level through frequent feeding and eating food that cause slow and steady increases in blood sugar.