Quacks be like:

“Grains make you fat. Fruit makes you fat. Eating too little makes you fat. Vegetables make you fat. Sugar makes you fat.”  

So to get lean:

No grains, fruit, vegetables, or sugar, and lots of butter, red meat, and calories. Seems legit.

Look, eating GMO food doesn’t make people fat. Eating too much OMG food makes people fat.

Eating fructose doesn’t make people fat. Eating too much fructose (and thus calories) makes people fat.

Stress doesn’t make people fat. Eating too much food when stressed makes people fat.

Bad gut bacteria don’t make people fat. Feeding gut bacteria too much food makes people fat.

Eating from large plates and bowls doesn’t make people fat. Eating too much from large plates and bowls makes people fat.

Hormones don’t make people fat. Eating too much food when hormones are pumping up appetite makes people fat.

Eating at the wrong times of the day doesn’t make people fat. Spending too much time in the day eating makes people fat.

Genetics don’t make people fat. Eating too much food with genes that encourage overeating makes people fat.

Slow metabolisms don’t make people fat. Eating more food than their metabolism burns makes people fat.

Drinking alcohol doesn’t make people fat. Drinking and eating too many calories makes people fat.

And if you disagree with this message because you believe people aren’t responsible for how much food they put in their mouths due to their DNA, upbringing, socioeconomic circumstances, etc., you necessarily must also believe they’re not responsible for anything else they do—an untenable position, to put it delicately.