Effects of weight cycling and aging on body protein content in female wistar rats

• Published in: Nutrition research (New York, N.Y.) N.Y.), 1999-05, Vol.19 (5), p.741-748
• Main Authors: Jen, K-L.Catherine, LeClair, Elizabeth S., Buison, Anne, Pellizzon, Michael A.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Development. Metamorphosis. Moult. Ageing; Fat percent; Fundamental and applied biological sciences. Psychology; High fat feeding; Old; Protein percent; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Weight cycling; Young
• ISSN: 0271-5317; 1879-0739
• DOI: 10.1016/S0271-5317(99)00036-6

The effects of body weight cycling (WC) on body protein content are inconclusive. This study was designed to investigate the interactive effects of WC and aging on body protein content in female Wistar rats. Young (2.5 months old at the beginning of the study) and old rats (11 months at the beginning of the study) were divided, within each age category, into: 1) low fat (LF) ad-lib fed control group (LFA); 2) LF restricted fed group (LFR); 3) high fat (HF) ad-lib fed group (HFA); 4) HF restricted fed group (HFR); 5) HF fed, weight cycled group by gaining weight first (HFG); and 6) HF fed, weight cycled group by losing weight first (HFL). WC was achieved by ad-lib and restricted feeding of the HF diet so rats' body weight was cycling between baseline and 20% above or below the baseline level. This WC was repeated 3 to 5 times. At sacrifice, rats in restricted groups and cycling groups weighed the same. Old rats weighed significantly more than the young rats. There was no age effect on total and percent body fat, and on total protein content, although young rats tended to have higher percent protein than old rats. In the young groups, the protein percent was significantly lower in HFA, HFG and HFL groups as compared to all other groups within that age. In old rats, the protein percent of cycling groups was not different from other groups, with the exception that HFL group had significantly lower protein percent than that of the HFR group. Within each age category, the HFA group had significantly higher body weight and fat content than all other groups. Therefore, weight cycling starting at a young age, when accumulation of body protein is not yet complete, may deprive the body of the opportunity to lay down the normal amount of protein. This may have significant health implications for human teenagers engaging in weight cycling practice.