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As a nation, we are struggling with rising rates of obesity. Extra pounds affect every organ system in the body and contribute to many illnesses, including asthma, sleep apnea, diabetes, heart disease and cancer. While we recognize that obesity is a significant factor in many health conditions, we are still trying to fully understand what drives weight gain and what we can do about it. Three recent articles in scientific journals explore some of the underlying factors that contribute to obesity. The articles show that we must move beyond the strongly held societal beliefs that obesity is merely an issue of willpower and look for the deeper roots of the condition — in our genetics, how we are raised, and even the size of our plates.

Childhood Stress and Obesity

The Article: Gender, Stress in Childhood and Adulthood, and Trajectories of Change in Body Mass

The Findings: Researchers looked at the relationship between stress and body mass index, or BMI, across the lifespan. Using surveys of more than 3,600 people taken over a 15-year period, they examined the relationship between stress in childhood and adulthood on how much an individual weighed in adulthood. Rather than just asking individuals if they felt they had had a stressful childhood, the researchers asked about whether individuals had experienced specific events in their youth, including parental death or divorce, parents with mental health or substance issues, and economic problems. Adult stress was measured similarly, asking people whether they had experienced the death of a loved one, job loss, or had been a caregiver, among other questions.  

The study found that women with elevated stress in childhood tended to have higher BMIs, compared with women with fewer childhood stressors. They also found that stress in childhood was most closely linked to further weight gain as an adult than the level of stress in adulthood. Changes in stress in adulthood did not lead to significant changes in weight. Interestingly, stress in childhood or adulthood did not significantly affect weight for the men in the study.

Why might childhood stress set women up for obesity? Feeling stress is acutely uncomfortable, leading to both physiological and psychological changes, including anxiety and heightened alertness. Studies have shown that individuals may engage in certain behaviors, like overeating, in an attempt to alleviate those feelings, with some research suggesting that women in particular are more likely to reach for food for a degree of comfort.  

It’s in Our Genes

The Article: Obesity and Genomics: Role of Technology in Unraveling the Complex Genetic Architecture of Obesity

The Findings: The authors reviewed recent work to uncover the role of genetics in the development of obesity. Previous work, particularly reviews of twin and adoption studies, have begun to tease apart genetic end environmental factors in the development of obesity, and most have suggested that there is a strong genetic component to obesity. In rare cases, the connection between genes and obesity is a straightforward one, with a change in a single gene resulting in significant weight gain. When it was discovered that mice with a mutation in the leptin gene developed extreme obesity, it was thought that this would lead to a revolution in our understanding of human obesity and treatment. But while some individuals with obesity have mutations in leptin and related genes, that is actually extremely rare.

As technology has advanced, we have been able to move from looking at single genes to examining the entire genome. This enables us to find novel genes and groups of genes that may be related to obesity. For example, variations in a gene called the FTO gene have been consistently associated with increased BMI in a number of different populations. Rather than having direct involvement in a pathway linked to eating or nutrition, the FTO gene makes a protein that affects how other genes are expressed, giving a hint of just how complicated the genetic underpinnings of obesity are. While it would be nice if obesity came down to variants in single genes, making it easier to develop targeted interventions, it seems more likely that there are multiple genes at play that may vary on the individual level. Increasingly, research is focused on attempting to map this complex system of interactions. While the article is hopeful, it shows that we are far from a thorough understanding of the role of genetics in the obesity epidemic.

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