Valid points about money, but they’re primarily talking about calorie restriction and how metabolic adaptation eventually leads to weight loss stopping, because metabolism adapts to less energy and you can’t just keep ‘eating less’. If you’re familiar with the low carb community, this is what’s famously called the ‘Biggest Loser’ problem, referring to the TV show and how contestants lost a lot of weight through extreme calorie restriction—but their metabolism eventually slowed down and they couldn’t eat less, so—nearly everyone gained it all back.