A study on mice has found fat cells may encourage the spread of cancer tumours.
The Institute of Research in Barcelona found fat may act as an energy source for cancer cells, helping tumours spread between organs.
In the study, published in Nature, cancer was found to spread most aggressively in mice given a high-fat diet.
When the fat cells were blocked with antibodies, the spread of cancer was "significantly reduced" - however this didn't stop cancer cells from forming in the first place.
Melanoma, skin cancer, and lung and breast cancer are thought to be the cancers most able to spread through fat cells.
The Spanish scientists now hope to continue the study on 1000 people with cancer.
"If the team are able to go on to develop this antibody into a treatment for humans it could save thousands of lives every year," says Dr Lara Bennett, science communications manager at Worldwide Cancer Research.
It's hoped the antibody will be clinically trialled in four years' time.
However, a scientist from the University of Chicago has warned it is too early to tell people to avoid fatty foods, especially people with cancer who may need a high-energy diet.
Ernst Lengel - who was not involved in the study - told Scientific American that would sent a "very dangerous" message.