Thymic involution is the process by which the thymus shrinks with age and produces fewer T cells, impairing immunity and increasing the risk of infection in older adults. In addition, thymic involution increases the risk of cancer and autoimmunity with age.

However, research has identified some of the mechanisms of thymic involution and highlighted possible strategies to improve immunity:

• By activating PPAR-gamma, a protein that regulates fat metabolism, caloric restriction reduced the rate of thymic involution in mice and increased the number and diversity of circulating T cells.
• T cells from participants with obesity tended to be less diverse, a finding supported by a study in mice that found that diet-induced obesity increased immunosenescence, a type of advanced cell aging, and thymic involution in mice. This suggests maintaining a healthy weight may slow thymic involution and loss of T cell immunity.
• Stress increased the rate of thymic involution in...