An analysis has found that people who think too much about food could ruin their diet plans.

Huberts said that this is when justification processes become a slippery slope - as the reasons are often applied ad hoc, they no longer form strict rules that regulate when you stick to your diet and when you can cut yourself some slack.
A growing body of research has found that such justification can even come from performing well on a task or from doing good for others. In several studies, people who received positive feedback on a task were more likely to choose an unhealthy versus a healthy option.
Source-ANI