Fat by itself is very satiating, you'd struggle to rack up the calories eating purely fat unless you were really trying. However too much sugar without fibre wi

Fat by itself is very satiating, you'd struggle to rack up the calories eating purely fat unless you were really trying. However too much sugar without fibre will spike your blood sugar levels which triggers an insulin response, causing your body to effectively store any glucose in your bloodstream into muscle and fat cells[0]. The end result is you're hungry again and able to eat more calories. Combine that with a high fat diet and you have a recipe for obesity. When I used to weight train, during my cuts (weight loss phases), I had much more success with a high fat/low carb diet than I ever did calorie counting (which naturally makes you avoid fat since they have a higher calorie density). [0] Not an expert but this is my layman's understanding after reading lots of books on the subject.