A Simple Blood Test Could Someday Predict Obesity

Would you want to know that you are prone to obesity years before you show any evidence of having a serious weight problem? Sarah Leibowitz, an obesity researcher at Rockefeller University in New York, believes most people would want to have a “heads up” that they will likely become obese so that they can make preventative lifestyle changes (curbing calorie intake, getting adequate exercise, etc.) before they’re faced with excess weight. If Leibowitz’s early work with fat rats translates to humans, a simple blood test could be all that’s needed to get such an advanced warning that you’re inclined towards obesity.

Telltale Signal in the Bloodstream

As Leibowitz explains, rats that are prone to obesity harbor a telltale signal (elevated blood levels of fats known as triglycerides) in their bloodstream that can be detected years before they gain excess weight—and she’s suggesting the signal is probably also present in humans. She said that after the study’s rats are fed a high-fat meal, the sharp rise in triglyceride levels is “almost 100% predictive of (an inclination towards future) obesity.” If the same pathway proves true in humans, testing blood fat levels while one is in their early teens could help predict whether they will likely have to deal with obesity later on.

Leibowitz suggests that diets in which more than 30% of the day’s calories come from fat can trigger a vicious cycle: increased fat intake raises triglyceride levels and stimulates the complex circuitry within the brain to crave still more high-fat foods—ultimately causing more and more weight gain. Dr. Joel Elmquist, an assistant professor of neurology specializing in obesity research at Harvard Medical School in Boston, calls this hypothesis “very plausible.” Noting that the mechanisms of appetite and weight gain are similar in rats and people, he adds that “while we have to see how the experiments bear out, it is certainly worthy of future study.”

More Than 1 in 5 American Adults Are Obese

Anyone with a body mass index—a ratio between height and weight—of 25 is considered overweight, and anyone with a body mass index of 30 or higher is considered obese. According to the National Center for Health Statistics, more than 1 in 5 American adults are obese, and more than half are overweight.

There are major advantages to knowing you’re one of those who should carefully count calories, monitor fat intake, and include a regular exercise routine to better ensure maintaining a normal, healthy weight, Leibowitz said. “Sure, you can splurge on cake and chocolates now and then, but then you’ll know you’ll have to cut back a bit later in the week.”

Leibowitz emphasized how “once overweight, it’s so hard to lose the pounds—it’s much better to avoid them in the first place.” Whether the elevated triglycerides are a valid marker for obesity has yet to be determined, she said. But in either case, they likely indicate a cause for action.

Complex Genetic-Environmental Interactions

Leibowitz said it’s unclear why triglyceride levels shoot up in response to fat intake for some but not for others, but she believes it’s all part of complex genetic-environmental interactions. According to her theory, fats travel through the bloodstream to the brain and stimulate genes that promote both overeating and fat storage.

In her study, Leibowitz also observed that the rats with high triglyceride levels produced large quantitites of small molecules called peptides. A high count of peptides is another factor in obesity as it serves to stimulate the appetite, especially an appetite for fats.

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