Have you ever heard that you should never eat fewer than A NUMBER of calories every day, like 1,200, 1,500 or 1,800?

If you do eat less than this, legend goes, many misfortunes can befall you, including . . .

  • Metabolic damage
  • Extreme hunger
  • Malnutrition
  • Hormonal disruptions
  • Muscle loss
  • Mood disturbances
  • Menstrual irregularities

The list jabbers on.

I often hear from people who are concerned by this theory because an evidence-based formula or calculator is telling them to eat what they believe is a “dangerously low” number of calories every day.

Fortunately, a true universal caloric minimum would be much lower than this because many people simply don’t burn as many calories as they think they do, and even when calories are inappropriately low, the purported consequences are often overblown.

For example, a 5’5”, 130-pound woman who exercises 1-to-3 hours per week burns about 1,700 calories per day, and if she wanted to lose about 1 pound of fat per week (moderate weight loss), she’d need to eat about 1,200 calories per day.

If we make her 5’10” and 160 pounds, though, her total daily energy expenditure (TDEE) rises to nearly 2,000 calories per day, and if we increase her exercise to 4-to-6 hours per week, it reaches 2,300 calories per day. Then, if we calculate her daily calorie target for 1 pound of fat loss per week, we get 1,800 calories—virtually lean gaining for her smaller and more sedentary self.

It works the same in men. A 5’7”, 160-pound guy exercising 1-to-3 hours per week burns about 2,100 calories per day, whereas a 6’3”, 200-pound man exercising 4-to-6 hours per week burns almost 3,000 per day.

So, saying that nobody should ever eat less than some arbitrary amount of calories per day like saying they should never drive slower than 55 miles per hour on the highway. What if they have engine trouble? What if there’s traffic? What if it’s raining pitchforks? Such advice is too schematic.

Just how low should you go when cutting, though? There is a caloric threshold you shouldn’t cross, isn’t there?

Yes, because if you restrict your calories too heavily, you won’t “damage” your metabolism, detonate your hormones, disintegrate your muscle, or otherwise derange your physiology, but negative side effects often associated with semistarvation (very-low-calorie) dieting can become more pronounced.

Based on the findings of research on the effects of energy availability on athletic men and women, when cutting, I recommend no less than 8-to-10 calories per pound of body weight per day regardless of activity level (and 10-to-12 per pound per day works well for most people).

This lower limit allows for (reasonably) rapid fat loss without any of the disadvantages caused by extreme dieting.

And what of the nutritional component of dieting? Can you develop irritating insufficiencies or even debilitating deficiencies by eating significantly less food than usual?

Not if you get most of those calories from relatively unprocessed and wholesome foods like lean protein, fruits, vegetables, legumes, whole grains, seeds, and the like. And if you really want to ensure your body is adequately nourished when cutting, include a high-quality multivitamin in your cutting regimen.

But the bottom line is that there is no cut-and-dried cutoff for how low your calories should be—the answer depends on your circumstances, preferences, and goals, and there’s no physiological “tripwire” that sends your body into starvation mode when your calories get too low.

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