Exploring the sense and nonsense of food and health

Born to be Fat?

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Identical twins

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Weight loss in the obese has been a hot topic since 1959 when Jules Hirsch first began his experiments at Rockefeller University.  The conventional wisdom now days is usually “eat less, exercise more”, but if one would examine the work of Jules Hirsch and Rudolph Leibel, then research physicians at Rockefeller University more carefully, a better understanding of the frustrations of the obese would ensue. Every dieter knows that keeping pounds off is even harder than losing the weight in the first place. In 1995 Hirsch and Leibel published a landmark study that explained why lost weight tends to return. It’s a matter of metabolism: reduce a person’s body fat, and metabolism slows so that the body burns fewer calories to carry out the same tasks, and weight comes back. New England Journal of Medicine 1995, 332:621 -628.

Dr. Hirsch’s study gave about 50 people in several experiments who had been obese most of their lives with a rigorous four week diet of a liquid formula providing only about 600 calories a day.  All lost weight but all regained their weight much to his surprise.

Before the diet began, the subjects’ metabolism was normal- number of calories burned was no different from that of non-fat people.  When the obese lost weight, they were burning as much as 24% fewer calories than calories consumed by those who were naturally thin.

The Rockefeller subjects also had a psychiatric syndrome, called semi-starvation neurosis.  They dreamed and fantasized about food; they were anxious and depressed; they hid their food in their rooms; they often binged.  The same results occurred in another landmark study by Ancel Keys called the “Minnesota Experiment” during World War II.   Prolonged semi-starvation caused most of the volunteers to experience periods of severe emotional distress and depression.  Participants exhibited a preoccupation with food, both during the starvation period and the rehabilitation phase. Sexual interest was drastically reduced, and the volunteers showed signs of social withdrawal and isolation. The participants reported a decline in concentration, comprehension and judgment capabilities, although the standardized tests administered showed no actual signs of diminished capacity. There were marked declines in physiological processes indicative of decreases in each subject’s basal metabolic rate (the energy required by the body in a state of rest), reflected in reduced body temperature, respiration and heart rate.

These results indicate that body weight may be inherited, so Albert J. Stunkard, MD, PhD, then at the University of Pennsylvania,  investigated the question. He examined a Danish registry of adoptees from 1927 and 1947 that included records and names of the biological parents and adoptive parents along with their heights and weights.  He ended up with 540 adults with an average age of 40 who had been adopted in the first year of life.  His conclusions were published in The New England Journal of Medicine in 1986, which stated that the adoptees were as fat as their biological parents, and their degree of fatness had no relation to their adoptive parents.  So nature had won over nurture.

Dr. Stunkard published another study in 1990 in The New England Journal of Medicine using twins to support this theory. Based on a Swedish Twin Registry, he studied 93 pairs of identical twins who were reared apart, 154 pairs of identical twins who were reared together, 218 pairs of fraternal twins who were reared apart, and 208 pairs of fraternal twins who were reared together.

The identical twins had nearly identical body mass indexes, whether they had been reared apart or together.  There was more variation in the body mass indexes of the fraternal twins.

These conclusions also support the often-discussed set point theory.  Researchers have confirmed that after weight losses or gains the body adjusts its metabolism to restore the original weight.  Energy expenditure increases after weight gain and decreases after weight loss. This theory helps to explain why it is so difficult for an underweight person to maintain weight gains and an overweight person to maintain weight losses.

The message is so at odds with the popular conception of weight loss – i.e. eat less and exercise more. Jeffrey Friedman, an investigator at the Howard Hughes Medical Institute since 1986, and director of the university’s Starr Center for Human Genetics was quoted in 2000 in the journal Science: “Those who doubt the power of basic drives, however, might note that although one can hold one’s breath, this conscious act is soon overcome by the compulsion to breathe.  The feeling of hunger is intense and, if not as potent as the drive to breathe, is probably no less powerful than the drive to drink when one is thirsty.  This is the feeling the obese must resist after they have lost a significant amount of weight.”


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