> Someone may have a desire or intention to lose weight. But unless they lose the weight they lack incentive.

Here are just some of the incentives overweight people have to lose weight:

They'll look better, to themselves and others. They'll have more clothing options. They'll feel better. They'll be healthier. They'll have drastically lower odds of many future heath problems. They'll live longer which means they can spend more time being with their loved ones.

Those are all incentives. Everyone who is obese has those incentives, even though different individuals may assign different values to them. Even with all those incentives that hasn't stopped the obesity problem. incentives don't incite action, but they can encourage them.

incentive noun [ C or U ] Something that encourages a person to do something by offering them a reward (https://dictionary.cambridge.org/dictionary/english/incentiv...)

You can have a ton of encouragement, but that doesn't mean it will be enough to incite a behavior. What definition of incentive are you using?