Every public health pronouncement leads with the large headline "the obesity epidemic is growing worse." This heads up applies not just to the U.S., but to the world in general. National Geographic even coined the term "globesity" to capture this reality.
Any time there is a widespread epidemic the sleuths look for the causative agent. The demons behind malaria, smallpox, polio, and AIDS have been identified. Such identification has done much good. There is no more smallpox. There is less malaria, and polio and AIDS hopefully are on the endangered list. But all reports about the epidemic of obesity indicates that it is getting worse instead of better.
Is obesity contagious ? Can you catch it from somebody else? The fact that it displays a marked family clustering indicates that obesity may be catching. A recent Atlantic story asks "can your family make you fat?"(1)
Many, many studies have shown a tight correlation between the parental and childhood BMIs. This of course seems to point to a genetic contribution. Yet exhaustive studies have failed to identify an obesity gene. The present consensus indicates that there are at least 56 different genes that are involved in the epidemic of fat kids.
So what else do parents give beside genes? How about the environment?
Even the prenatal environment causes us to ponder. (2) Maternal weight gain during pregnancy is a large risk factor. Children of obese mothers have a much higher incidence of adult obesity.
After delivering a baby other environmental forces intrude. Identified as prominent features are the number of meals eaten as a family and the amount of time spent at TV and video game watching. Parental stability is critical. Children of divorced or separated parents have higher incidences of obesity. (3) A number of social studies indicate that the child's sense of self efficacy, the ability to control one's emotions is a causative feature. Levels of family stress, of whatever type, modify the predisposing elements. It seems obvious that stress in and of itself is causative
And of course I recall the occasion of my 51st birthday that I spent in the delightful company of the Bushmen on the Kalahari Desert. After a day of general carousing and focusing on their click-click language we gathered around the campfire for my birthday party: much singing, clapping, and good cheer. As the embers started to die down in the fire the chief rounded up our attention for his benediction of clicks. " Happy Birthday to you" sounds different with clicks. At the conclusion of his speech there was much applause and smiles. I inquired of our guide, "what did he say?" He said "Prof. Bortz, we wish you a long life, and may all your children be fat." "What?" I asked. "May all your children be fat." I was stunned, but then I reflected that such a well wishing by a Kalahari Bushman was the most generous thing that he could muster. Their existence is daily threatened because of starvation. So getting enough to eat is precious. Incidentally there are no fat Bushmen.
So as we survey the question as to whether obesity is contagious we must look way back and recognize that we current earthlings may have caught our obesity from our paleo ancestors. Our genes have not changed in these millennia but the Bushmen don't have junk food or video games.
Poor thin them. Poor fat us.
References
1)Khazam O. Can your children make you fat?
The Atlantic 2/12/2014.
2)Salsberry,PJ, Reagan PB. Taking the Long View: the prenatal environment and early adolescent obesity.Res. Nurs.Health 2007, 3:297-307.
3)Augustin,J.,Kim R. 2013 Informing Policy for children at risk. J.Applied Research on Children 4: 1-10.