New Year’s resolutions and dieting seem to go hand-in-hand. Setting a personal goal to lose weight and exercise more may jump-start the New Year but “February frustration” can derail even the most determined. Scientists in Sanford-Burnham’s Diabetes and Obesity Research Center recently shared their expertise on the causes of weight gain and the metabolic challenges that make it so hard to keep off the extra pounds. Their insights on genetics, diet, metabolism and lifestyle were included in a four-part series called “What’s making Americans so fat?” that ran in the Orlando Sentinel beginning January 1. Medical reporter Marni Jameson spoke with national obesity experts to compile a list of 40 reasons for why 60 percent of U.S. adults are obese or overweight.
“It’s not gluttony, and it’s not lack of willpower,” says Dr. Steven Smith, scientific director of the Florida Hospital – Sanford-Burnham Translational Research Institute for Metabolism and Diabetes. “No scientist in the field will say the problem is strictly one of willpower,” he says. “It’s a result of the way our genes are interacting with an environment that is stacked against them.”
Here’s an excerpt of how the experts weighed in:
Genetics: “About half our propensity to gain weight or not is inherited,” says Dr. Steve Smith. Though genes haven’t changed much in thousands of years, we have seen a rapid change in the environment, and that has interacted with our genetic propensity toward obesity. “Your genes won’t make you fat unless you put them in the wrong environment.” In other words, obesity is a result of the way certain genes interact with an environment stacked against them.
Aging: Most Americans get heavier as they age. An aging population skews the overall percentage of obesity up, says Smith. Americans gain an average of a pound a year. Today the median age of Americans is 36.9, up from 32.9 years in 1990.
Ethnicity: “The prevalence of obesity is higher among African-Americans and Hispanics because of how their genes and cultures interact with our environment,” Smith says. From a demographics standpoint, the rise in these minority populations has contributed to the uptick in the nation’s obesity rate. Black women are at the highest risk of any group, according to the Department of Health and Human Services’ Office of Minority Health. Four out of five black women in the U.S. are overweight or obese.
Birth order: Siblings born later in the lineup tend to be fatter than firstborns or those born earlier, Smith says. Researchers think this is because moms tend to weigh more with each pregnancy, and therefore have more circulating insulin with each subsequent pregnancy. This is in turn passed along to the baby and future generations.
Weight regain: As hard as it is to lose weight, keeping pounds off is even harder. Once again, biology works against you. Many mechanisms in the body kick in to encourage the body to regain lost weight. “The hormone leptin, for instance, which is produced in fat cells, stimulates appetite while slowing metabolism,” Smith says. This leads many in the field to think that sustaining weight loss during the long haul may require hormone therapy.
Fat mothers: “If your mom was obese while she was pregnant with you, you’re marked,” says Philip Wood, professor at Sanford-Burnham Medical Research Institute in Lake Nona. “You will have an uphill battle fighting off excess weight and its ill effects, even if you’re adopted and raised by slim parents.” The rising field of epigenetics is revealing how diet and the environment are reprogramming the genes we’re dealt at conception.
Brown fat: Why some people get fat and others – don’t regardless of what they eat – may lie in part in the color of their fat, says Sheila Collins, professor at Sanford-Burnham Medical Research Institute in Lake Nona. Bodies store two kinds of fat: white (fairly inactive tissue that acts as a storage bank) and brown (highly active tissue that actually burns calories and white fat), she says. How much brown fat we have is probably determined by our genes. It appears to play a role in body-fat composition and in keeping weight off. Collins and others are looking for ways to make the brown fat we do have more active and also to increase it. Based on new work from her lab, she thinks exercise will likely play a role.
Lack of sleep: The obesity epidemic parallels the rise in sleep deprivation, and that’s no coincidence, says Dev Sikder, assistant professor at Sanford-Burnham Medical Research Institute, in Lake Nona. Many metabolic hormones, including insulin, which regulates fat storage, rise during the day and fall at night. This regulation is part of a normal, healthy circadian rhythm. Sleep deprivation, however, forces insulin to stay at high levels, which triggers the body to store fat.
To read the complete Orlando Sentinel series, follow these links:
Part 1: How diet contributes to obesity.
Part 2: The role played by heredity.
Part 3: How lifestyle changes have affected our weight.
Part 4: The influence of environment and government policies.