© C.J. BURTON/CORBIS
Obesity and associated health consequences are the greatest public-health challenges of our time. Worldwide, an estimated 1.5 billion people tip the scales as overweight—300–500 million of whom are obese—placing nearly a quarter of humanity at dramatically increased risk for diabetes, cardiovascular disease, and many types of cancer. While considerable scientific investments have barely begun to slow the expansion of our waistlines, they have yielded unexpected physiologic insights, perhaps the greatest of which is the discovery that proper metabolic function requires a previously unsuspected level of cooperation between the cells that make up each internal organ and that organ’s resident leukocytes.
For almost 2 centuries, the stereotypical appearance of basic human tissues—muscles with their long, cabled cells; kidneys with their cauliflower floret–shaped structures—have been a familiar ...
