Begley cites some possible reasons other than diet and exercise for the weight gain of animals and, by extension, us:
- The type of bacteria in our gut - more efficient bacteria wring more calories out of our food than do less efficient bacteria. In this case, efficiency is not our friend.
- Lack of sleep, which increases the appetite-stimulating hormone ghrelin, and decreases the hormone leptin that suppresses our appetite when we’ve eaten enough.
- Environmental chemicals such as BPA that stimulate fat-cell production.
- Home heating, which lessens the need for the body’s calorie-consuming heat production.
- Home air conditioning, which lessens the appetite-suppressing effect of environmental heat.
- Infection with adenovirus-36, which causes obesity in lab animals and is correlated with obesity in humans.
- The lack of internal parasites due to modern sanitary practices. If parasites eat some of our food, less of it can be packed on as fat. If they partake of our bodies, then energy must be consumed for repair. This assumes the kind of parasites that are relatively harmless other than consuming some of our food or body tissue.
There is no doubt that our health benefits from exercising regularly and eating a healthy diet without excess calories. However, we must continue to look for other contributing factors in order to effectively deal with and counteract the continued rise in overweight and obesity that threatens to undermine the gains we’ve made in improving our health and increasing our lifespan.