Compound in Tomatoes May Help Stave Off Weight Gain

Study in zebrafish suggests lycopene helps the liver process fats

Baltimore (April 25, 2025)—New research suggests that lycopene, which gives fruits like tomatoes and watermelons their bright red color, supports healthy liver functioning and may help prevent weight gain. Researchers will present their work this week at the 2025 American Physiology Summit in Baltimore. The Summit is the flagship annual meeting of the American Physiological Society (APS).

Lycopene is an antioxidant, anti-inflammatory compound that is naturally produced by some plants. It is also available as a dietary supplement, although supplements are not evaluated for safety or effectiveness by the U.S. Food and Drug Administration and the potential health impacts of lycopene supplements are not well established.

The researchers’ interest in studying the impacts of tomato consumption and lycopene on obesity was sparked by a previous study that showed dietary estrogen supplements prevented zebrafish from becoming obese despite being overfed. Since lycopene and other compounds found in tomatoes affect some of the same chemical pathways as estrogen, the scientists wondered if eating tomatoes could have a similar effect.

“This study is unique because we are assessing interactions between tomatoes, estrogens and obesity prevention mechanisms,” said the study’s first author Samantha St. Clair, PhD, assistant professor of biology at Northern State University. “Since tomatoes are a rich source of the antioxidant lycopene, we are assessing whether the obesity protection in tomato-supplemented fish stems in part from reduced inflammation in the liver.”

Researchers conducted a series of experiments in which they fed zebrafish a normal or high-fat diet along with various combinations of tomato extract, estrogen supplements and lycopene supplements. They found that fish consuming a high-fat diet supplemented with a tomato extract were more effectively protected from weight gain than fish on a high-fat diet supplemented with dietary estrogen. Also, fish that were fed a high-fat diet supplemented with both estrogen and lycopene had lower blood sugar levels compared with fish consuming a normal diet. This finding suggests that lycopene consumption improves the breakdown of fat in the liver. 

The researchers also found that the benefits of tomato consumption happened fast, showing a significant difference in metabolism after just one week. “We are really excited about this one week time point. If a relatively short-term intervention tweaks metabolism to protect against weight gain, this implies that folks would be able to make some small adjustments to their daily diet and see benefits in a few weeks’ time,” said St. Clair.

The team is conducting further analyses to track changes in gene expression involved in inflammation, fat processing and estrogen metabolism at different time points and with different types of supplements. “This data will enable us to paint a broader picture of how tomato consumption alters liver metabolism to help prevent diet-induced obesity,” said St. Clair.

The researchers also plan to further study how lycopene content and impacts on metabolism may vary among different types of tomatoes.

NOTE TO JOURNALISTS: The American Physiology Summit will be held April 24–27, 2025, in Baltimore. To schedule an interview with the researchers, conference organizers or presenters, or to request abstract A-0348, “Tomato Consumption Mitigates Diet-induced Obesity in Zebrafish,” contact APS Media Relations or call 301.634.7314. Find more highlights from the meeting in our Newsroom. 

Physiology is a broad area of scientific inquiry that focuses on how molecules, cells, tissues and organs function in health and disease. The American Physiological Society connects a global, multidisciplinary community of more than 10,000 biomedical scientists and educators as part of its mission to advance scientific discovery, understand life and improve health. The Society drives collaboration and spotlights scientific discoveries through its 16 scholarly journals and programming that support researchers and educators in their work.