Fasting switches fat cells into energy burners
White fat cells store energy. That is their function. But what if you could switch them into burning energy instead, like brown fat cells do? Intermittent fasting appears to do exactly that, through an unexpected branch of the immune system.
Researchers published findings in eLife showing that intermittent fasting activates a specific group of immune cells called type 3 innate lymphoid cells (ILC3s). These cells release a signalling molecule called IL-22, which prompts white fat cells to undergo a process known as ‘beigeing’. In this process, white fat cells acquire characteristics of brown fat cells and begin burning energy rather than storing it. The study appeared in eLife.
Beige fat as an intermediate state
White adipose tissue accumulates when energy intake exceeds expenditure. Brown adipose tissue has more mitochondria and burns energy as heat. Beige adipose tissue is an intermediate form: ordinarily stored fat that, under certain conditions, takes on properties of brown fat. This switching process, known as browning of white fat, has long been recognised as a potential way to improve metabolic health, though the mechanisms were not fully understood.
The involvement of ILC3 cells and the cytokine IL-22 as a link between intermittent fasting and fat tissue remodelling is a new piece of that puzzle. It connects the immune system directly to how fat tissue responds to dietary patterns.
Relevance for aging
Fat tissue biology is closely tied to aging. As people get older, white fat storage tends to increase while brown and beige fat decline. This contributes to metabolic problems such as insulin resistance. If intermittent fasting can partly reverse this pattern through immune signalling, the implications for longevity research are worth noting. It should be mentioned that this is a correction to an earlier publication, meaning some details may have been revised. The core finding is not disputed in the correction.
Whether the same mechanism operates in humans and whether it produces long-term health benefits requires further study.
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