A BMI of 16 is very rare. It's unlikely it was always that low for him. Assuming someone starts with a BMI of 22-24 and then diets to get it to 16, this would likely would req. fewer than 1900 even if the calculator says so, due to metabolic adaption and the breakdown of the calculations at extremes .
Of course it would take less than 1900 to get there. But it would take around 1900 to stay there, according to our models of basal metabolic rates. And it turns out that this person stays there at 1900, so our conclusion is that the BMR model we're using fits this data point.
It's possible that for some people at such extremes commonly available models would break down, but clearly for this person, they haven't. And while BMIs of 16 are relatively rare, so are 6 foot tall males that eat an average of 1900 calories for years.
Ultimately if you're trying to use this case to show that the models are inaccurate, that's not what this case does, it's actually remarkably close to what is predicted and if anything would be better used as evidence in their favour.
"I eat the same thing twice a day, seven days a week, 365 days a year," says Pomerleau, of his diet of 1,200 calories a day. "It's a lot of veggies with olive oil-based salad dressing, a lot of mixed fruits, almonds and hazelnuts, and flaxseed oil for omega-3 fatty acids."
.Bob Cavanaugh, a 54-year-old landscaper from Morehead, N.C., has trimmed his intake to two meals a day, totaling 1,500 calories. Breakfast consists of one cup of quick oats, two tablespoons of toasted wheat germ, one cup of skim milk and blueberries. For dinner, he eats vegetables, fruit and a small portion of fish. "I'm hoping to see my great, great grandchildren," he says.
Mr. Cavanaugh's diet may sound extreme, particularly since at 5-feet 9-inches tall and 158 pounds, he isn't overweight. But over the next several years, if the monkey results hold up, they could represent a major shift in how we view food and nutrition. The U.S. Department of Agriculture says the average sedentary woman should eat 1,600 calories a day and the average man 2,200 -- benchmarks already significantly overshot by most Americans.
Bob Cavanaugh's case is not relevant, as he has relatively recently made these changes, and therefore isn't at equilibirium. Same goes for your third guy, the BMI is from 2004/2009, while his caloric intake is from 2019 and was after a 5 year taper (and was therefore higher in 2009).
Your first example. Pomerlau, weighed only 121 pounds - that's a BMI of 18 - and lost 5kg/year, which means that if he did eat 1200 calories, he almost certainly wasn't at equilibrium yet, either - it would take a few more years.
