Brain activity and response to food cues differ in severely obese women, study shows

The brain’s reward centers in severely obese women continue to respond to food cues even after they’ve eaten and are no longer hungry, in contrast to their lean counterparts, according to a recent study by a multidisciplinary team at UT Southwestern Medical Center.

The study, published recently in the journalĀ Obesity, compared attitudes and the brain activity of 15 severely obese women (those with a body mass index greater than 35) and 15 lean women (those with a BMI under 25).

MRI images of the study participants were taken before and after a meal. Both groups showed significantly increased activity in the neo- and limbic cortices and midbrain when they were hungry. After eating, however, that brain activity dropped among lean participants while continuing in their obese counterparts.

Even after eating and reporting they were full, the severely obese women continued to react to pictures of food in much the same way they had when fasting, as exhibited in brain scans.

“Before or after the meal, they’re just as excited about eating,” said Dr. Nancy Puzziferri, Assistant Professor of Surgery at UT Southwestern and senior author of the study. “It seems they have an instinctive drive to keep eating.”

While the appeal of pictured food dropped 15 percent for the lean women after they ate, the severely obese women showed only a 4 percent decline, based on brain scans using functional magnetic resonance imaging (fMRI) to measure brain activity. After eating, activity in regions in the prefrontal cortex and posterior cingulate cortex significantly changed in the lean group, but not in the obese group. The obese study participants maintained activation in the midbrain, one of the body’s most potent reward centers.

Study participants had fasted for nine hours prior to testing. They were asked to rate their level of hunger or fullness, then given a brain scan as they viewed pictures of food. Again, they were asked to rate their level of hunger. Over the next hour, the women were fed a meal of lean beef or chicken, potatoes or rice, green beans, canned peaches, and iced tea or water. After eating, the participants went through another battery of hunger/fullness ratings and fMRI scans while exposed to pictures of food.

The obese women showed sustained “hungry” brain activation, even though they reported the same increase in satiation as their lean counterparts.

So what does this mean for obese people?

“These findings may explain why some people with severe obesity report an underlying drive to eat continually despite not feeling hungry,” said Dr. Puzziferri, who specializes in bariatric and weight loss surgery. “In contrast, lean women when full will either stop eating or just sample a food they crave. It’s just not a level playing field – it’s harder for some people to maintain a healthy weight than others.”

The severely obese women in the study, who weighed between 202 and 316 pounds, were candidates for bariatric surgery to lose weight. The study is following these women after surgery to determine if their brain activation patterns change.

The study was conducted at UT Southwestern and VA North Texas Health Care System. Funding for the research came from UT Southwestern and the National Institutes of Health.

7 Comments

  1. Question is more if the pattern change for the severely obese that had the will power to stop eating too much and start exercising at least a little.

    Many have made this experiment without getting “severely” obese:

    – get pretty fat/well enough above your normal BMI

    – start exercizing and stop eating too much. At this stage even when you’ve eaten and no longer hungry you will still feel like eating more food than you should.. tada.

    – keep being good at this, yes, its hard for a while

    – return to normal BMI

    – after a couple of weeks, once full, you feel like you do not want any more food at all and wont be as excited by the food.

    I mean come on. Only if people who voluntarily do not eat too much yet still show the brain has strong food cue would prove the theory in this article. Surgery to lose weight will change nothing at all. Are these guys paid by the food and medical industry?

    Because obvious is obvious.

    • Jessie James on

      It’s not that easy to stop you ever tell somebody addicted to Heroin to just stop? It doesn’t work. Why do i say that? because sugar just like heroin makes Dopamine in your brain. It also stops the full signal getting put to your brain. It gets blocked. New study from Robert H. Lustig, MD

      • but again it doesn’t mean that you can’t. people get cured. its not overnight and its painful but it works.
        generally involves friends strapping them to a bed for month because hospitals cant do this legally – but it still works.

    • Hilarious to see someone with a normal food response try to give advice to people with brains who function differently. Maybe a future study will demontrate brain differences in people with compassion or just fundamental intelligence and we will better understand your response.

      • but thats exactly the point…
        its easy to put everything on “genetics” but the reality is that you can train your brain any way you want. Its just that you don’t. Like you probably don’t do real, consistent exercise either.

  2. Jessie James on

    A doctor already found the reason why they still want to eat after they are full, but they don’t want it to get out because it well hurt somebody’s money. It’s the damn sugar in everything.