For anyone trying to lose weight, there's a truth we can all universally acknowledge that better health is often positioned as a numbers game. Hit the right number, and all your health problems will magically resolve, so the logic goes. Yet increasingly, science is revealing that losing weight may not be a silver bullet after all. In a mouse study published in the journal Science，looking specifically at an inflammatory（炎症的）eye condition linked to obesity called macular degeneration（黄斑退化）， researchers found the struggle for better health doesn't necessarily begin and end with weight loss.

Researchers conducted experiments on mice that were fed a high-fat diet for 11 weeks, making them gain weight The mice were then put on a diet of low-fat food for 9 weeks, making them lose weight. Another group of mice only ate the low-fat diet as a control. Researchers shot lasers into the eyes of both the yo-yo dieter mice and the control mice to encourage atypical blood vessel（非典型性血管）growth，a mark of macular degeneration. 

Among the mice that had gained and then lost weight, there was about 40 percent more atypical blood vessel growth than their stable diet peers. Driving the growth appeared to be macrophages（巨噬细胞）. In the yo-yo dieter mice, these cells had been reprogrammed to cause inflammation. Taken together, these cells appeared to have an outsize role in atypical blood vessel growth in the eyes. Meanwhile, in the mice fed only a low-fat diet, inflammatory changes were absent. The results suggest that eating a high-fat diet that causes weight gain, even if followed by weight loss, leaves an inflammatory mark on mouse macrophages. 

The research comes during a period of renewed interest in anti-obesity drugs. But medicines that help people shed pounds do not treat inflammation linked to a history of weight gain. "How to engage these findings with medicine interventions is a challenge," says Bapat, head of the research.