The FDA claims a sedentary 40 year old man needs 2400 calories a day, the same as a 17 year old incidentally. [1] Or that everybody just needs 50g of protein a day. [2] Then there's the fat vs sugar food pyramid nonsense that led to more than half a century of health degradation.

[1] - https://www.fda.gov/media/112972/download

[2] - https://www.fda.gov/food/nutrition-facts-label/daily-value-n...

The government shapes diets both through guidance (food pyramid, “plates”, etc) and regulation. For example, a major criticism revolves around farm bill payouts that incentivize corn production, leading to cheap fructose that finds its way into everything.