Sex differences in obesity and the regulation of energy homeostasis

Abstract

SummaryObesity prevalence is generally higher in women than in men, and there is also a sex difference in body fat distribution. Sex differences in obesity can be explained in part by the influence of gonadal steroids on body composition and appetite; however, behavioural, socio--cultural and chromosomal factors may also play a role. This review, which evolved from the 2008 Stock Conference on sex differences in obesity, summarizes current research and recommendations related to hormonal and neuroendocrine influences on energy balance and fat distribution. A number of important gaps in the research are identified, including a need for more studies on chromosomal sex effects on energy balance, the role of socio--cultural (i.e. gender) factors in obesity and the potential deleterious effects of high--fat diets during pregnancy on the foetus. Furthermore, there is a paucity of clinical trials examining sex--specific approaches and outcomes of obesity treatment (lifestyle--based or pharmacological), and research is urgently needed to determine whether current weight loss programmes, largely developed and tested on women, are appropriate for men. Last, it is important that both animal and clinical research on obesity be designed and analysed in such a way that data can be separately examined in both men and women. Introduction The prevalence of obesity is higher in women than in men in most countries around the world (http://www. IOTF.org; accessed July, 2008). Although it has been suggested that evolutionary pressures predispose women to store excess fat for reproduction and lactation, the factors driving the greater propensity for excess body weight in women are not well understood. One line of research has focused on gonadal hormones, their influence on peripheral and central mechanisms that control appetite and body weight. Another line of research has focused on behavioural and social differences between men and women that relate to eating or activity behaviours. Pregnancy and menopause also have physiological and behavioural consequences on appetite and weight regulation that confer elevated obesity risk in many women.Despite the generally lower population prevalence of obesity in men, obese men are at substantial risk of obesity--related chronic diseases because of fat accumulation in abdominal, visceral depots. It has long been recognized that men and premenopausal women differ in their fat distribution, the so--called 'gynoid' and 'android' fat distribution. Because of the significantly increased cardiometabolic risk associated with abdominal fat in men (and postmenopausal women), it is important to understand mechanisms that determine where fat is accumulated. Recent research using molecular approaches and animal models has provided greater understanding of the role of sex hormones and other molecules on fat partitioning.Despite burgeoning research in this field, a number of important questions remain unanswered. What is the role of chromosomal sex and in utero effects on obesity? What specific effects do m...

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