> The further implication that a particular macronutrient ratio could cause obesity is particularly concerning. Weight gain/loss is determined strictly by whether someone consumes more or fewer calories than their body burns in a day. The ratio of macronutrients may effect other health indicators like lean body mass, but a diet of 100% sugar and fat will still lead to weight loss if the total caloric intake is lower than what the body requires thereby requiring the body to burn muscle/fat for energy[1].

Perhaps, but people in the real world don't usually carefully measure out a portion based on calories before consuming; they eat until they're not hungry anymore. So any food that is calorically dense but doesn't satisfy hunger is likely to contribute to obesity.

The government warns against fats and sugars for similar reasons here https://health.gov/dietaryguidelines/dga2010/dietaryguidelin...