ObjectivesTo describe new WHO 2020 guidelines on physical activity and sedentary behaviour.MethodsThe guidelines were developed in accordance with WHO protocols. An expert Guideline Development Group reviewed evidence to assess associations between physical activity and sedentary behaviour for an agreed set of health outcomes and population groups. The assessment used and systematically updated recent relevant systematic reviews; new primary reviews addressed additional health outcomes or subpopulations.ResultsThe new guidelines address children, adolescents, adults, older adults and include new specific recommendations for pregnant and postpartum women and people living with chronic conditions or disability. All adults should undertake 150–300 min of moderate-intensity, or 75–150 min of vigorous-intensity physical activity, or some equivalent combination of moderate-intensity and vigorous-intensity aerobic physical activity, per week. Among children and adolescents, an average of 60 min/day of moderate-to-vigorous intensity aerobic physical activity across the week provides health benefits. The guidelines recommend regular muscle-strengthening activity for all age groups. Additionally, reducing sedentary behaviours is recommended across all age groups and abilities, although evidence was insufficient to quantify a sedentary behaviour threshold.ConclusionThese 2020 WHO guidelines update previous WHO recommendations released in 2010. They reaffirm messages that some physical activity is better than none, that more physical activity is better for optimal health outcomes and provide a new recommendation on reducing sedentary behaviours. These guidelines highlight the importance of regularly undertaking both aerobic and muscle strengthening activities and for the first time, there are specific recommendations for specific populations including for pregnant and postpartum women and people living with chronic conditions or disability. These guidelines should be used to inform national health policies aligned with the WHO Global Action Plan on Physical Activity 2018–2030 and to strengthen surveillance systems that track progress towards national and global targets.

Insulin resistance is a major factor in the pathogenesis of type 2 diabetes in the elderly. To investigate how insulin resistance arises, we studied healthy, lean, elderly and young participants matched for lean body mass and fat mass. Elderly study participants were markedly insulinresistant as compared with young controls, and this resistance was attributable to reduced insulinstimulated muscle glucose metabolism. These changes were associated with increased fat accumulation in muscle and liver tissue assessed by 1 H nuclear magnetic resonance (NMR) spectroscopy, and with a ∼40% reduction in mitochondrial oxidative and phosphorylation activity, as assessed by in vivo 13 C/ 31 P NMR spectroscopy. These data support the hypothesis that an ageassociated decline in mitochondrial function contributes to insulin resistance in the elderly.Type 2 diabetes is the most common chronic metabolic disease in the elderly, affecting ∼30 million individuals 65 years of age or older in developed countries (1). The estimated economic burden of diabetes in the United States is ∼$100 billion per year, of which a substantial proportion can be attributed to persons with type 2 diabetes in the elderly age group (2). Epidemiological studies have shown that the transition from the normal state to overt type 2 diabetes in aging is typically characterized by a deterioration in glucose * To whom correspondence should be addressed. gerald.shulman@yale.edu. [11][12][13]. Increases in the intracellular concentration of fatty acid metabolites have been postulated to activate a serine kinase cascade leading to defects in insulin signaling in muscle (14-17) and the liver (18), which results in reduced insulinstimulated muscle glucose transport activity (14), reduced glycogen synthesis in muscle (19,20), and impaired suppression of glucose production by insulin in the liver (11-13).To examine whether insulin resistance in the elderly is associated with similar increases in intramyocellular and/or liver triglyceride content, we studied healthy elderly and young people that we matched for lean body mass (LBM) and fat mass. All study participants were non-smoking, sedentary, lean [body mass index (BMI) < 25 m 2 /kg], and taking no medications. Sixteen elderly volunteers (ages 61 to 84 years, 8 male and 8 female) were screened with a 3-hour oral glucose (75 g) tolerance test and underwent dual-energy x-ray absorptiometry to assess LBM and fat mass (21). One elderly man was excluded from the study because of an abnormal glucose profile. Thirteen young volunteers (ages 18 to 39 years, 6 male and 7 female), who had no family history of diabetes or hypertension, were matched to the older participants for BMI and habitual physical activity, which was assessed by means of an activity index questionnaire (22). All participants underwent a complete medical history and physical examination, as well as blood tests to confirm that they were in excellent health (23).Young and elderly participants had similar fat mass, percent fat mass, and LBM (Table 1...

Skeletal muscle insulin resistance is a common feature of obesity, dyslipidaemia and arterial hypertension, and it is an important predisposing factor for Type II (non-insulin-dependent) diabetes mellitus and premature cardiovascular disease [1]. Evidence has been provided that lipids could have an important role in insulin resistance: i) lipid oxidation is increased in insulin resistant states [2] and ii) increase of plasma concentrations of non-esterified fatty acids (NEFA) decreases skeletal muscle glucose uptake and glycogen synthesis [3]. The impact of intramyocellular lipid (IMCL) content on insulin sensitivity has previously been examined from muscle biopsies. The results showed that IMCL are an important source of energy within the muscle [4] and that increased IMCL content is associated with impaired insulin-stimulated glucose uptake in rats [5] as well as in healthy humans [6,7] and in those with Type I (insulin-dependent) diabetes mellitus [8].Proton nuclear magnetic resonance ( 1 H NMR) spectroscopy now enables non-invasive quantification of the IMCL content in humans [9±11]. This study was designed: i) to examine the cross-sectional relation between IMCL and whole body insulin sensitivity in non-diabetic humans by using non-invasive localized proton NMR spectroscopy and ii) to compare the relative contributions of IMCL, BMI and Diabetologia (1999) Summary Recent muscle biopsy studies have shown a relation between intramuscular lipid content and insulin resistance. The aim of this study was to test this relation in humans by using a novel proton nuclear magnetic resonance ( 1 H NMR) spectroscopy technique, which enables non-invasive and rapid (~45 min) determination of intramyocellular lipid (IMCL) content. Normal weight non-diabetic adults (n = 23, age 29 2 years, BMI = 24.1 0.5 kg/m 2 ) were studied using cross-sectional analysis. Insulin sensitivity was assessed by a 2-h hyperinsulinaemic (~450 pmol/l)-euglycaemic (~5 mmol/l) clamp test. Intramyocellular lipid concentrations were determined by using localized 1 H NMR spectroscopy of soleus muscle. Simple linear regression analysis showed an inverse correlation (r = ±0.692, p = 0.0017) between intramyocellular lipid content and M-value (100±120 min of clamp) as well as between fasting plasma non-esterified fatty acid concentration and M-value (r = ±0.54, p= 0.0267). Intramyocellular lipid content was not related to BMI, age and fasting plasma concentrations of triglycerides, non-esterified fatty acids, glucose or insulin. These results show that intramyocellular lipid concentration, as assessed non invasively by localized 1 H NMR spectroscopy, is a good indicator of whole body insulin sensitivity in non-diabetic, non-obese humans. [Diabetologia (1999) 42: 113±116]