I recently got drunk with a medical man; An American as it happens, who works in one of the many US bases in Airstrip One.
The servicemen in his care grow fatter and fatter. He tells them to eat less and exercise more.
He knows perfectly well that that won't work long-term, and yet he tells them to do it anyway. It's the party line.
And of course, this advice will work short-term.
Of course it will.
Calories In, Calories Out.
You can starve yourself thin, and if you're facing a yearly medical and you're going to get thrown out of the army because you're so fat, you probably should.
But the minute that medical is passed, the weight comes straight back on. And next year the problem is worse.
You can starve yourself thin, but you can't starve yourself healthy.