From Figure Athlete
Either increasing leptin, keeping it from dropping, or increasing our sensitivity to it would be a positive thing en route to avoiding the negatives of dieting.
It's long been recommended that dieters employ periodic "cheat," reefed, or high carb days. The reasoning for their benefit is generally psychological. However, in addition to the mental relief, taking diet breaks can effectively be used to boost leptin. This, in turn, can temporarily raise your metabolism, increase fat burning, and help reduce the pitfalls of dieting. This explains why a plateau in fat loss will often be broken after a diet break.
From a nutritional standpoint, the primary stimulator of leptin is glucose intake. In women, an 820-calorie meal that was 80% carbohydrates increased leptin levels 50% over five hours and 100% over nine hours. Fat, fructose, and protein don't have the same effect on leptin expression. The same sized meal consisting of 80% fat only caused increases of 15 and 25% (4).
In another study, people were massively overfed, consuming approximately 8,000 calories of fast food over 12 hours and noting leptin increases of 40% (5). It should be mentioned that only 35% of their diet came from carbohydrates. In the same study, lean individuals consuming approximately 25 calories per pound of bodyweight and who also increased their bodyweight by 10% noted a three-fold increase in leptin over five weeks.
Taking all of this into consideration, we can see the benefits of implementing periodically higher calorie intakes. Not only does short-term carb feeding lead to leptin expression, but it also leads to preferential glycogen storage and carbohydrate oxidation, rather than fat gain.