Bringing Science to the Study of Obesity: The Number of Fat Cells and Their Size

Jules Hirsch is his laboratory

Obesity has a long history of being blamed on a lack of personal willpower when it comes to food. But Jules Hirsch (1927- ) pioneered in bringing a scientific approach to the problem by investigating biologic and biochemical differences between the obese and people of normal weight. The resources of the Rockefeller Hospital made it possible to research these questions with human subjects. In the 1960s Hirsch made the surprising discoveries that the individual fat cells of obese people are larger than those in people of normal weight, and moreover, the very obese have more fat cells.

Hirsch also found that, after months of dieting in the hospital (patients were fed precisely defined formula diets), fat cells shrank in size, but their number remained the same. It was difficult for his obese patients to stay lean after dieting—as soon as they began consuming more calories, their fat cells refilled, and they re-gained weight. Along with other research, this led to the widely accepted adipose cell hypothesis: fat cells develop early in life and their number is fixed.

When an obese person loses weight, the fat cells shrink but their number is uncharged. Illustration by Karina Aberg

Jules Hirsch received his undergraduate education at Rutgers University and earned the MD at Southwestern Medical School, University of Texas - Dallas (1948). After an internship at Duke University Hospital and residencies at Upstate Medical Center in Syracuse, NY, he joined the Rockefeller Institute in 1954. Hirsch served as Physician-in-Chief of the Rockefeller University Hospital from 1992 to 1996, and chairman of the Institutional Review board from 1984 to 1996. He has been president of the Association for Patient-Oriented Research and the American Society for Clinical Nutrition, and contributed as an editor or editorial board member to more than a dozen journals. Among many honors and awards, Hirsch has been elected to the Institute of Medicine, and he received the Stunkard Lifetime Achievement Award from The Obesity Society in 2006.

Selected Publications

Hirsch J, Knittle JL, and Salans LB. Cell lipid content and cell number in obese and nonobese human adipose tissue. J Clin Invest, 1966, 45: 1023

Salans LB, Knittle JL, and Hirsch J. The role of adipose cell enlargement in the carbohydrate intolerance of human obesity. J Clin Invest, 1967, 46: 1112

Hirsch J and Gallian E. Methods for the determination of adipose cell size in man and animals. J Lipid Res, 1968, 9: 110-119

Further Reading

Hirsch J. Obesity: matter over mind? Cerebrum, 2003, 5: 7-18