If you're eating fewer than 1,200 calories per day, your workouts will suffer and the constant stress on your body can lead to muscle loss and slow your metabolism, as we reported in 10 Things You Don't Know About Calories. If you're trying to eat super healthy, you might be surprised at how few calories you're actually eating—try tracking your daily intake with a food tracking app and make sure you're fueling your body, not depriving it of nutrients.
It's been seven months since I started my diet, and two months since I left it. I've begun eating a light lunch, and having an occasional small snack. I'm still at 175. But I never want to lose the delicious edge of hunger before dinner, or the floating sensation when I walk. Moving takes less energy now, so I have more energy. I no longer feel like a spherical physicist. And for losing weight, dieting sure beats cleaning animal stalls.
A reasonable daily diet for an adult is 2,000 food calories. That's 8.36 megajoules per day, or about 100 joules per second -- in other words, 100 watts. Most of that ends up as heat, so you warm a room as much as a bright light bulb. Cut your consumption by 600 calories per day and you'll lose a pound of fat every week. Most diet experts consider that a reasonable goal. Don't drop below 1,000 calories per day, or you might get lethargic. But at 1,400 calories per day, you can easily maintain an active life.