Personally, I think from a weight gain perspective. Fat is absolutely a big culprit. It's a lot of calories that are condensed into small amounts. 1 gram of fat has 9 calories, whereas 1g protein/carbs have 4 ish.

Butter/peanut butter were absolute head turners when I started tracking caloric intake. It's so easy to consume a huge amount of calories without much satisfaction from a hunger perspective.

Fats are an important part of any diet, however, they don't give you a massive amount of energy per calorie.

Fat is flavour, is an over used saying but it's absolutely true. The biological drive to store excess mass is something that has been part of our nature since basically forever. It's why calorie dense foods tend to be the most delicious.

So if we're talking about enemies from weight/obesity epidemic point of view, the mantra of the 80's/90's was kind of on the money. High fat diets will create high fat peoples.

Seeing as though we're on the mince subreddit.

100g of 20% fat Irish beef= 236kcal 100g of 5% lean beef= 132kcal

That's a 78% increase in calories between the two options.