Fructose causes obesity.
Fructose by its self is addicting through "reward circuits".
Fructose causes insulin resistance directly.
Fructose blocks leptin signaling directly, and high insulin causes blocking of leptin signaling.
Glucose, usually with the fructose, causes insulin to rise, and the insulin causes fat storage, since the fructose has caused insulin resistance, and high insulin causes leptin resistance.
The first step in any weight loss is get rid of all fructose, ie no fruit, sugar, none.
Second step is to get rid of all wheat, and sources of glucose, also addicting, but by a different pathway.