title: Seasonal variation in insulin sensitivity in healthy elderly people.
abstract: OBJECTIVE
  There is a seasonal variation in the incidence of diabetes mellitus and cardiovascular diseases. However, there is very little information about the seasonal variation in insulin sensitivity. We report the seasonal variation in insulin sensitivity in a group of elderly subjects followed for 1 y.
  
  
  METHODS
  Healthy elderly (>/=70 y) subjects living independently were included. Fifty percent of subjects received a daily nutritional supplement that provided 400 kcal, 15 g of protein, and 50% of vitamin daily reference values (DRVs). Those receiving and not receiving supplements were randomly assigned to a resistance exercise training program. Every 6 mo (winter, summer, and winter), body composition was measured by dual-energy x-ray absorptiometry and blood samples were used to measure serum lipids, fasting and postprandial glucose, and insulin levels.
  
  
  RESULTS
  One hundred eight subjects (31 supplemented and trained, 28 supplemented, 16 trained, and 33 without supplementation or training) completed the follow up. Higher homeostasis assessment of insulin sensitivity, postprandial insulin, and fasting triacylglycerol levels were observed during the summer than during the winter. Body fat increased steadily during the study period, and fat-free mass did not change. Serum low-density lipoprotein cholesterol decreased significantly in the supplemented and trained group and increased in the non-intervention group.
  
  
  CONCLUSIONS
  In this group of elderly subjects, insulin resistance and triacylglycerol levels were higher during the summer. Nutritional supplementation and training had a positive effect on serum low-density lipoprotein cholesterol.
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile. dbunout@uec.inta.uchile.cl
authors.forename: Daniel
authors.initials: D
authors.lastname: Bunout
authors.forename: Gladys
authors.initials: G
authors.lastname: Barrera
authors.forename: Pia
authors.initials: P
authors.lastname: de la Maza
authors.forename: Vivien
authors.initials: V
authors.lastname: Gattas
authors.forename: Sandra
authors.initials: S
authors.lastname: Hirsch
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000187:drug effects / Q000502:physiology; D002318:Cardiovascular Diseases / Q000097:blood* / Q000453:epidemiology; D008078:Cholesterol, LDL / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000453:epidemiology; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D005215:Fasting; D005260:Female; D006801:Humans; D015994:Incidence; D007328:Insulin / Q000378:metabolism*; D008297:Male; D019518:Postprandial Period; D011446:Prospective Studies; D012621:Seasons; D014280:Triglycerides / Q000097:blood; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D008078:Cholesterol, LDL; D007328:Insulin; D014280:Triglycerides; D014815:Vitamins