Dr. David B. Allison

While not disputing other claims that disparities in the availability of healthy foods or the lack of financial means to purchase them may influence a person’s ability to remain at a healthy weight, Allison proposed there could be an additional factor that may cause someone to further tip the scales. His theory posits that perhaps the stress that comes with a low perception of one’s current social stability or future prospects might lead someone to turn to food and accrue additional energy in the form of body fat to provide a buffer against energetic insecurity.

Allison began by looking at relationships between children and their parents, both natural and adoptive. While he found no apparent genetic correlation to account for a tendency to become obese, he did instead find evidence consistent with the effect of being raised in a home of low socioeconomic status and the likelihood of the children becoming obese as they grew up.

With this data, Allison began focusing on behavior. He took several steps back to examine the ways in which instinctual behaviors in other species might signal that similar impulses are at play in human beings. What he found may add another layer to the already complex discussion about what is making Americans so fat.

“In studying social status, scarcity and weight gain in birds, we find that birds low in the social hierarchy gain weight and fat when food is somewhat scarce,” he said.

What’s interesting, Allison continued, is that the birds that collect the most food are the furthest down the flock’s social ladder. While birds that have higher social standing may not feel concerned because they can simply steal food from those who have stockpiled, the less-important birds may feel stressed to over-collect to ensure their own survival in lean times. Faced with the uncertainty of not knowing whether food will be plentiful in the future, the birds may expend much of their time on food gathering and consuming and less on other activities.

Allison looked at other species besides man for insights into obesity.

In an anecdotal turn that the audience found telling, Allison compared the impulse to guard resources and cut out unnecessary expenditures of energy to what happens in an economic downturn within academia.

“When money is tight at a university, you’ll see some of the workforce laid off while the school moves to protect the endowment,” he said. “You keep the fat and cut the muscle.”

The same phenomenon occurs within the research community, he said.

“In lean times in research, people will say they’re hedging their bets and will apply in many more places for funding. With approximately the same number of principal investigators, overall grant applications will go way up.”

Allison also drew connections between energy intake, weight and longevity, noting that BMI, or body mass index, tends to have a U-shaped relationship with how long someone lives. While the very obese and the very skinny tend to not live quite as long as their more average counterparts, the idea of losing weight as a general rule doesn’t necessarily mean someone in that middle ground may live longer, though the day-to-day improvement in energy and attitude are certainly great perks.

However, as shown in mouse models, some caloric restriction may have a lightly beneficial effect, he said. But there’s a catch. The studies suggest that it is not only the amount of energy consumed that affects longevity, but also the perception of the amount consumed and the perception of the caloric richness of the environment. If the body remembers eating more in the same setting and enjoys eating the type of food it has grown accustomed to, it will hunger for those same foods at the old levels, sparking a brain-body reaction that holds out hope for the good ol’ days.

Paraphrasing another author, Allison quipped, “So if you want to live longer, eat less and don’t enjoy it.”

Anyone interested in attending future lectures in the NIDDK series is encouraged to contact Dr. Giovanni Cizza to be added to the mailing list. He may be reached at Giovanni.Cizza@nih.gov, or by calling (301) 496-8711.