Researchers have studied a hunter-gatherer tribe, the Hazdas, and have discovered that despite much higher levels of activity compared to Western lifestyles, their metabolic rate is identical to ours.  Even after corrections for height and weight, all Hazda men and women aged 18 to 75 burn calories at the same rate of people in the West.

This has shone a bright light on the importance of diet, especially when it comes to portion size. According to one of the chief researchers, Dr. Pontzer,

“This to me says that the big reason that Westerners are getting fat is because we eat too much – it’s not because we exercise too little. Being active is really important to your health but it won’t keep you thin – we need to eat less to do that.”

Energy expenditure happens to be almost identical across the physiological board.