Hormone Leptin Affects Food's Appeal

A new British study shows that the fat hormone leptin may
affect whether people desire, dismiss, and delight in certain foods.

Leptin is a hormone that's mostly made by the body's fatty tissue. It plays
a role in regulating weight and appetite.

The new British study centers on two teens who have a rare genetic condition
that blocks their body from making leptin. The researchers included I. Sadaf
Farooqi, MD, PhD, and Paul Fletcher, MBBS, MRCPsych, PhD, of the University of
Cambridge.

First, the 14-year-old boy and 19-year-old girl got their brains scanned
with functional magnetic resonance imaging (fMRI) after fasting and 30 minutes
after eating a meal.

During the brain scans, the teens saw a series of 150 pictures.

The pictures included 100 pictures of foods, including cakes, ice cream,
puddings "and other things that people generally report as being
'mouth-watering,'" as well as bland foods such as potatoes, plain noodles,
and broccoli, Fletcher tells WebMD via email.

The remaining 50 pictures showed trees, cars, boats, and other things that
aren't foods.

Yum or Yawn?

The researchers displayed each picture for four seconds. When a food picture
popped onto the screen, the teens rated how much they liked and wanted that
food.

Next, the teens got leptin to treat their leptin deficiency.

One week later, the teens repeated the brain scans after fasting and after
eating a meal. Once again, they rated their interest in the food images
displayed during the brain scans.

Before leptin treatment, the teens wanted the foods that they saw during the
brain scans more than they did after leptin treatment.

They also reported being less hungry after fasting and fuller after eating
the meal following leptin treatment, compared to their hunger and fullness
ratings before receiving leptin.

The brain scans show that certain areas of the brain were particularly
active when the teens saw pictures of foodsB before leptin treatment. Those
brains were less active -- and more typical of people without leptin deficiency
-- after leptin treatment.

The type of food also made a difference. For instance, the brain scans
showed a small area of brain activity when a picture of broccoli was displayed,
and a bigger area of activity when a strawberry was shown.

The scientists conclude that leptin affects brain areas involved in desiring
and enjoying foods. In short, leptin may affect whether the brain says
"Yes, please," or "No, thanks," to foods people see.

The study appears in the journal Science's early online edition,
called Science Express.

By Miranda Hitti
Reviewed by Louise Chang
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