Scientists may have found what triggers belly fat as we age: a newly identified stem cell that emerges during aging and supercharges the body's production of brand-new fat cells. Researchers at City of Hope, working with UCLA, reported the discovery in the journal Science, framing it as a potential biological driver of middle-age weight gain and a promising target for future anti-obesity therapies.
Many people watch their waistline expand with age even when the number on the scale barely moves. "People often lose muscle and gain body fat as they age, even when their body weight remains the same," said co-corresponding author Qiong (Annabel) Wang, Ph.D. That extra abdominal fat is more than a cosmetic concern, as it has been linked to slower metabolism, accelerated aging, type 2 diabetes, heart disease, and other chronic conditions. Until now, exactly why fat concentrates around the midsection has remained unclear.
New fat cells, not just bigger ones
The team focused on white adipose tissue, the body's main fat-storage tissue, and on adipocyte progenitor cells (APCs), stem cells that mature into fat cells. Scientists already knew that existing fat cells enlarge with age, but the researchers suspected the body was also manufacturing entirely new ones.
To test that, they transplanted APCs from young and older mice into young mice. The results were striking:
- APCs from older animals generated large numbers of new fat cells.
- APCs from young mice placed into older mice produced relatively few.
- The fat-making ability tracked with the cells, not the host animal's age.
That pattern suggested the aggressive fat-producing capacity was built into the older cells themselves. "While most adult stem cells' capacity to grow wanes with age, the opposite holds true with APCs," said study author Adolfo Garcia-Ocana, Ph.D., describing it as early evidence that bellies expand with age because of the APCs' high output of new fat cells.
A new age-related cell and the LIFR signal
Single-cell RNA sequencing showed that APCs are largely quiet in young mice but become highly active in middle age. As the mice aged, some APCs transformed into a newly identified population the team named committed preadipocytes, age-specific (CP-As), which proved especially effective at producing fat.
The researchers traced the process to a signaling pathway called the leukemia inhibitory factor receptor (LIFR). "Our research indicates that LIFR plays a crucial role in triggering CP-As to create new fat cells," Wang said, noting that young mice do not need this signal to make fat while older mice do. That difference makes LIFR an appealing point of intervention, because blocking it might switch off the runaway fat production without disturbing normal metabolism in younger tissue. You can follow more breakthroughs like this in our science coverage.
Why it matters for humans
Analyzing human tissue from people of different ages, the team found cells closely resembling CP-As, present in greater numbers in middle-aged individuals and strongly able to generate new fat. That suggests the same mechanism operates in people, not just mice, which is the bar any potential therapy has to clear.
The next steps are to track these cells in animal studies, study how they behave in humans, and explore ways to block or eliminate them. If researchers can interrupt the CP-A and LIFR pathway, the long-term hope is a treatment that prevents age-related belly fat at its source rather than chasing the symptoms. The metabolic-health angle ties directly into our health reporting on diabetes and weight.
Frequently asked questions
What actually causes belly fat to increase with age?
The study points to adipocyte progenitor cells that become highly active in middle age and turn into a new cell type, CP-As, which churn out fresh fat cells, especially around the abdomen.
Could this lead to a new weight-loss drug?
Potentially. The researchers identified the LIFR signaling pathway as a target, and future work aims to block the CP-A cells, but no therapy exists yet and human trials would be required.
Does this mean diet and exercise do not matter?
No. The findings explain a biological driver of age-related fat gain, but excess belly fat is still linked to metabolism, diabetes, and heart disease, where lifestyle remains important.
