Carbohydrates: Edited by Luc Tappy and Bettina MittendorferLack of regular physical exercise or too much inactivityThyfault, John Pa,b,c; Booth, Frank Wb,d,e,f,gAuthor Information aHarry S Truman Memorial VA Hospital, USA bDepartment of Nutrition and Exercise Physiology, USA cDivision of Gastroenterology and Hepatology, Department of Internal Medicine, USA dDepartment of Biomedical Sciences, USA eDepartment of Medical Pharmacology and Physiology, USA fDalton Cardiovascular Research Center, USA gHealthy Activity Center, University of Missouri, Columbia, Missouri, USA Correspondence to John P. Thyfault, PhD, Assistant Professor and Health Scientist, Harry S. Truman Memorial VA Hospital, Division of Gastroenterology and Hepatology, Departments of Nutrition and Exercise Physiology and Internal Medicine, University of Missouri, Columbia, MO 65201, USA Tel: +1 573 882 9818; fax: +1 573 882 0185; e-mail: email@example.com Current Opinion in Clinical Nutrition and Metabolic Care: July 2011 - Volume 14 - Issue 4 - p 374-378 doi: 10.1097/MCO.0b013e3283468e69 Buy Metrics Abstract Purpose of review To discuss the current data that acute periods of physical inactivity are harmful to health. Recent findings Bed rest prescribed for recovery from clinical conditions causes changes in thousands of mRNAs in leg muscles within days. Humans genetically more susceptible to metabolic disorders (low birth weight babies and type 2 diabetic offspring) are as, or more, susceptible to further metabolic dysfunction by the environmental perturbation of bed rest, as compared with healthy controls without these risk factors. High daily accumulations of sitting are not only associated with enhanced metabolic risk, but current findings report that increased sitting time leads to a reduction in insulin sensitivity. Reductions in walking or in ambulatory activity (lower step numbers taken by healthy humans) reduce insulin sensitivity and insulin signaling through Akt in skeletal muscle. Summary New findings using human models of physical inactivity (bed rest, increased sitting time, and reduced daily ambulatory activity), extend pre-existing research showing that transitioning to physical inactivity rapidly reduced metabolic health. Modern technological advances that remove standing, walking, and major limb movement initiate metabolic dysfunctions that likely play a fundamental role in the development of obesity and type 2 diabetes. © 2011 Lippincott Williams & Wilkins, Inc.