Food insecurity as a cause of adiposity: evolutionary and mechanistic hypotheses

Abstract

Food insecurity (FI) is associated with obesity among women in high-income countries. This seemingly paradoxical association can be explained by the insurance hypothesis, which states that humans possess evolved mechanisms that increase fat storage to buffer against energy shortfall when access to food is unpredictable. The evolutionary logic underlying the insurance hypothesis is well established and experiments on animals confirm that exposure to unpredictable food causes weight gain, but the mechanisms involved are less clear. Drawing on data from humans and other vertebrates, we review a suite of behavioural and physiological mechanisms that could increase fat storage under FI. FI causes short-term hyperphagia, but evidence that it is associated with increased total energy intake is lacking. Experiments on animals suggest that unpredictable food causes increases in retained metabolizable energy and reductions in energy expenditure sufficient to fuel weight gain in the absence of increased food intake. Reducing energy expenditure by diverting energy from somatic maintenance into fat stores should improve short-term survival under FI, but the trade-offs potentially include increased disease risk and accelerated ageing. We conclude that exposure to FI plausibly causes increased adiposity, poor health and shorter lifespan. This article is part of a discussion meeting issue ‘Causes of obesity: theories, conjectures and evidence (Part II)’.

Breaking down silos: the multifaceted nature of obesity and the future of weight management

“…Experiencing lower social status is related to a variety of physiological and behavioural changes including chronic and/or acutely increased cortisol, blood pressure, heart rate, visceral adiposity deposition, cardiovascular disease and shortened life span among various animal models [21][22][23][24][25][26][27][28]. Experimentally mimicking conditions of human food insecurity in an avian model through limited and unpredictable access to food promotes metabolic disturbances and weight gain [29]. These findings parallel emerging observations in humans [30].…”

“…Investigation of the social and demographic factors explaining between-person differences in body weight and weight gain at a population-level is needed. Beyond dietary composition, psychosocial stress, low socioeconomic status, structural racism leading to health inequities and food insecurity impact biology and in part explain differences in body weight and weight gain [29]. It is not entirely clear why investigations into nonbiological bases for obesity (e.g.…”

Dietary Sodium and Potassium Patterns in Adults with Food Insecurity in the Context of Hypertension Risk

“…The lack of access to healthy food or uncertainty in obtaining it may cause changes in physical activity behaviors, which in turn, may contribute to chronic diseases such as obesity and hypertension. 31…”

Models of body weight and fatness regulation

“…Another interpretation, however, is that the UIP is not rigidly fixed but sensitive to local predation risk conditions. Indeed, we assume such flexibility in experimental studies where the predation risk is manipulated and a body weight response predicted [48][49][50][51]. Primates may be able to perceive that in captivity their predation risks are very much reduced and the corresponding UIP may move upwards in response.…”

“…The level of fat storage in many small animals seems to be flexible in the face of changes in the risk of predation [45][46][47][48][49][50]. Studies changing the risk of starvation have been successful in birds [51] but have proved less successful in small mammals (e.g. [52]).…”