A recent Canadian study has found certain BMI ranges to be more or less correlated with mortality, and quite counter-intuitively the study found that being overweight to mildly obese is the least risky – even somewhat less risky than having a normal BMI.
- Underweight, BMI less than 18.5; relative risk (RR) = 1.73, a significantly increased risk of death
- Overweight, BMI 25-30; RR = 0.83, a significantly decreased risk of death
- Obesity class I, BMI 30-35; RR = 0.95, neutral
- Obesity class II+ , BMI over 35; RR = 1.36, an increased risk of death
2)…the “overweight” are either muscular (rare) or in the sweet spot of temporarily being protected from the metabolic syndrome by their fat cells (this is the typical chunky guy on the street); and that those who are fatter than that, “obesity class II+”, are beyond protection (which only goes so far) and die early because of it.
However, and this is the kicker, once one has controlled for the metabolic syndrome (or put everyone on a paleo diet for 12 months), a different health equation goes into effect, which kicks these Western BMI studies in their soft underbellies.
Hunter-gatherers’ BMIs are typically in the lower range of what’s considered normal in Western contexts, and their body fat is roughly 10% for males, and 20% for women.
However, given hunter-gatherers’ gold standard health (as documented for example here recently, and in numerous other places) wich by far surpasses what’s considered normal in Western populations, it would be absolutely wrong for these hunter-gatherers to conclude that they should pack on extra weight (aside from muscle), say by eating some pasta or bread, to reach the BMI range with the lowest observed mortality risk by the standard of studies on Western corn-fed, metabolically deranged, people.
Conversely, what non paleo people in general should do is to rid themselves of the metabolic syndrome by adopting modern paleo principles including some high intensity exercise, and let their BMIs go wherever they need to go in that process. (Fat loss towards aesthetic satisfaction is usually part of the same package, but may require more tweaking.)