Weight Gain and Weight Loss in a Traditional African Society

Weight Gain and Weight Loss in a Traditional African Society

The Massas is an ethnic group in Northern Cameroon that subsists mostly on plain sorghum loaves and porridge, along with a small amount of milk, fish and vegetables (1, 2).  They have a peculiar tradition called Guru Walla that is only undertaken by men (2, 1):

This social institution, aimed at prestige acquisition, includes a massive overfeeding representing twice or threefold the habitual daily intake.

It lasts two months, during which they are overfed on sorghum, milk, fish and vegetables (mostly sorghum, but with an increased ration of milk as well).  They eat beyond the point of nausea, day and night, and expend as little energy as possible.  Calorie intake exceeds 8,000 kcal per day.  According to two detailed studies of nine Massas, by the end of Guru Walla, they had gained about 37 pounds (17 kg), mostly as fat* (2, 3).

What happened after they stopped overeating?  When they returned to their typical diet, which contains 75% carbohydrate, 11% fat, and 15% protein, the investigators found something interesting (3):

Rapid and substantial decreases in body weight and fat were observed in all subjects during the first 3.5 mo after the cessation of overfeeding. Subsequently, a more progressive decrease was noted up to the last measurement session. Thirty months after the end of Guru, the group had lost all of the overfeeding-induced weight gain.

This supports two ideas that may be starting to sound familiar:

1. Body fat mass is regulated in both directions (i.e., both increases and decreases are opposed)**.  This is supported by numerous overfeeding and underfeeding studies in both humans and rodents. 
2. Plain, repetitive starchy foods do not lead to fat gain and can support fat loss.

* This is less fat gain than expected due to the energy intake, suggesting "substantial thermogenesis" in response to the overfeeding.  Their bodies appeared to have mounted a compensatory response aimed at countering fat gain. 

** According to this hypothesis, obesity represents an increase in the "setpoint" around which fat mass in regulated.  This Guru Walla study is especially interesting because it looks at body fat regulation in a non-industrial society, which should have well functioning homeostasis mechanisms that have not been damaged by industrial living.  As fatness is prized in this society, they had no incentive to deliberately lose fat after Guru Walla.