Enhanced lipogenesis after fasting

345 Pershing Drive Oakland, CA 94611 E-mail: sngershoff{at}netzero.net

Dear Sir:

Wyatt and Hill (1) in their editorial about the excellent article by Weinsier et al (2) ask "whether it requires more physical activity to prevent weight regain than to prevent weight gain." In the 1960s, Harry Antoniades and I conducted a series of studies involving insulin and a protein with a higher molecular weight that we called bound insulin, which now, I believe, is called insulin-like growth factor. We extracted and partially characterized bound insulin from human serum and from a rat liver perfusate to which we had added insulin. In one of our studies with Huber et al (3), we reported that the epididymal fat pads of rats deprived of food for 4 d and then refed ad libitum showed a marked increase in lipogenesis compared with the fat pads from control rats in the presence of glucose and either insulin or bound insulin. Although we only reported data after 7 d of refeeding, I recall observing enhanced lipogenesis in the rats refed for 20 d. I wrote in our article, "It would seem reasonable to ask whether the rapid accumulation of fat often observed in people after a period of dieting might not in part be the result of increased ability to synthesize fat." This might answer, at least in part, the questions raised by Wyatt and Hill.

REFERENCES

1. Wyatt HR, Hill JO. Let’s get serious about promoting physical activity. Am J Clin Nutr 2002;75:449–50.
2. Weinsier RL, Hunter GR, Desmond RA, Byrne NM, Zuckerman PA, Darnell BE. Free-living activity energy expenditure in women successful and unsuccessful at maintaining a normal body weight. Am J Clin Nutr 2002;75:499–504.
3. Huber AM, Gershoff SN, Antoniades HN. The effect of fasting and refeeding on isolated rat adipose tissue activity in the presence of crystalline and "bound" insulin. Metabolism 1965;14:619–24.