ReviewThe food-insecurity obesity paradox: A resource scarcity hypothesis
Introduction
Low food security is associated with obesity in some circumstances (reviewed in [1], [2]). Low food security, defined as, “reports of reduced quality, variety, or desirability of diet. Little or no indication of reduced food intake,” by the USDA, does not involve hunger, whereas very low food security, defined as, “Reports of multiple indications of disrupted eating patterns and reduced food intake,” is accompanied by hunger [3]. The prevalence of low food security has risen in the United States in the last 15 years, and was 10.7% of households in 2001, and peaked at 14.9% in 2011 following a spike during the Great Recession [4]. It is not well understood if low food security plays a causative role in the development of obesity, and if it does, what the mechanisms may be.
There are two predominant, related hypotheses that have been proposed to explain this link in the literature:
- 1.
Low food security is associated with obesity because of the high calorie, palatable food consumed by low food secure populations [5], [6].
- 2.
Low food security is associated with obesity because of the limited knowledge, time, and resources that low food-secure populations experience to engage in healthful eating and exercise.
Both hypotheses are descriptive, but not probative or mechanistic in nature, as an explanation for the relationship between low food security and obesity. For substantial weight gain to occur, energy intake must be greater than energy expenditure on a long-term, chronic basis. There is a physiologically regulated, adaptable system that is designed to resist weight change.
Therefore, although documenting increased intake of high-energy, palatable foods or reduced physical activity in low food secure populations may document crucial parts of a mechanism, neither is a probative mechanistic explanation. Concluding that the intake of high calorie foods is sufficient to explain weight gain in low food secure populations is similar to concluding that individuals with Prader-Willi Syndrome gain weight because of the food they eat.
Though it is true that Prader-Willi Syndrome patients do consume more food than they require, this does not explain how this occurs on a chronic basis. The presence of food and the intake of food is a permissive, but not causative factor in their weight gain. The neurobiological mechanisms that cause increased food intake and weight gain are becoming well understood [7] so that therapeutics can be developed. Similarly, although an abundance of high calorie, palatable food may be a crucial permissive factor in the development of obesity in low food secure populations, its presence alone does not explain how low food security may drive the development of chronic positive energy balance. It is crucial to understand why and how low food secure populations gain weight, and what about low food security may be a fundamental driver of a net, chronic shift in the homeostatic regulation of energy balance. Such a mechanistic explanation may lead to more effective, cause-specific interventions.
The need for a more probative mechanism to explain the link between low food secure populations and obesity is clear from the lack of results from interventions that focus on food, resources, and knowledge to reduce weight gain. For example, when exercise facilities are made available to low SES populations, they are often not utilized [8]. Similarly, providing monetary resources or food caused weight gain in a low SES population in rural Mexico [9]. In another study, increasing food stamp funds to $2000/year had no effect on social BMI disparities [10]. It is plausible that such interventions are ineffective because they are not addressing the root mechanisms behind low food security's association with weight gain and obesity.
A probative, mechanistic explanation for the relationship between low food security and obesity can be proposed from intersections in findings from the fields of evolutionary biology, ecology, and obesity (Fig. 1). This “Resource Scarcity Hypothesis” suggests that perceived food insecurity, in a permissive environment where there is access to high calorie foods, may cause positive energy balance specifically in low social status individuals, but not in high social status individuals. Evidence suggesting this may be the case is reviewed in the following sections.
Section snippets
Social status and metabolic efficiency
Social status may be associated with low energy expenditure and metabolic efficiency. Since low food security tends to be associated with low social status, the role of social status in determining metabolic efficiency may contribute to the development of obesity in this population. Both animal and human studies suggest that low social status organisms may be more metabolically efficient.
For example, dominant mice have higher energy expenditure compared to subordinate mice, and are more obesity
Social status and excess food intake
Some evidence suggests that social rank may not only influence energy expenditure and metabolic efficiency, but energy intake as well. In animals, several experiments suggest social hierarchy has a causative influence on energy intake. Subordinate primates consistently consume more energy than dominant primates, regardless of diet type available (high or low-fat) [14]. This effect seems to be enhanced in the presence of a palatable, high fat diet. While both dominant and subordinate primates
Evidence that low food security influences body fat stores selectively in low social status individuals
In animals, an unpredictable or threatened food supply, in comparison to a predictable and secure food supply, has an influence on body weight and body fat stores, and the effect may be pronounced in low social status organisms in particular. For example, when female rats undergo just 5% energy restriction, they respond paradoxically by increasing fat stores [25]. In animals, experimental manipulation or natural circumstances that threaten the perception of food security increase body fat in
Potential physiological mechanisms linking low food security and social status with weight gain
Cortisol metabolism may mediate weight gain in response to low food security in low social status individuals. Low social status is associated higher basal cortisol levels, lower cortisol reactivity to acute stress, and a lack of cortisol habituation [34], [35], [36]. Impaired cortisol habituation is hypothesized to be a robust indicator of cumulative exposure to elevated cortisol that may accompany repeated exposure to stress [37]. Thus, higher basal cortisol, and lower cortisol habituation
Implications of the resource scarcity hypothesis in addressing the food insecurity-obesity paradox
If fat gain is a physiologically regulated, strategic response to low food security to ensure survival and reproduction, this would have several implications. First, interventions that seek to educate low food security populations about reducing energy intake and increasing energy expenditure may be insufficient to address the underlying problem, and therefore be unproductive. A lack of effect of such interventions is reflected in the literature [8], [9], [10].
On the other hand, the “Moving to
Acknowledgements
I would like to thank Drs. David Allison, Kathryn Kaiser, Gregory Pavela, and Michelle Cardel, as conversations with each of them have contributed in some way to the ideas presented in this paper. Also, this work was supported by Award Number P30DK056336 from the National Institute of Diabetes and Digestive and Kidney Diseases. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Diabetes and Digestive and
References (49)
- et al.
The food insecurity-obesity paradox: a review of the literature and the role food stamps may play
J. Am. Diet. Assoc.
(2007) - et al.
The economics of obesity: dietary energy density and energy cost
Am. J. Clin. Nutr.
(2005) - et al.
Relationship of hunger and food insecurity to food availability and consumption
J. Am. Diet. Assoc.
(1996) - et al.
Socioeconomic status differences in recreational physical activity levels and real and perceived access to a supportive physical environment
Prev. Med.
(2002) - et al.
Cash and in-kind transfers lead to excess weight gain in a population of women with a high prevalence of overweight in rural Mexico
J. Nutr.
(2013) - et al.
The modifying effects of Food Stamp Program participation on the relation between food insecurity and weight change in women
J. Nutr.
(2006) - et al.
Psychosocial stress induces hyperphagia and exacerbates diet-induced insulin resistance and the manifestations of the metabolic syndrome
Psychoneuroendocrinology
(2013) - et al.
Energy metabolism in African Americans: potential risk factors for obesity
Am. J. Clin. Nutr.
(1999) - et al.
Racial differences in the relation between uncoupling protein genes and resting energy expenditure
Am. J. Clin. Nutr.
(2002) - et al.
Quantifying food intake in socially housed monkeys: social status effects on caloric consumption
Physiol. Behav.
(2008)
Diet choice, cortisol reactivity, and emotional feeding in socially housed rhesus monkeys
Physiol. Behav.
Stress, dietary restraint and food intake
J. Psychosom. Res.
Stress may add bite to appetite in women: a laboratory study of stress-induced cortisol and eating behavior
Psychoneuroendocrinology
Individual weight change is associated with household food security status
J. Nutr.
Food insecurity is positively related to overweight in women
J. Nutr.
Subjective social status moderates cortisol responses to social threat
Brain Behav. Immun.
Social hierarchy and adrenocortical stress reactivity in men
Psychoneuroendocrinology
The NPY system in stress, anxiety and depression
Neuropeptides
Exploring mediators of food insecurity and obesity: a review of recent literature
J. Community Health
Definitions of Food Security
Food security in the United States
Satiety dysfunction in Prader-Willi syndrome demonstrated by fMRI
J. Neurol. Neurosurg. Psychiatry
Social stress and recovery: implications for body weight and body composition
Am. J. Physiol. Regul. Integr. Comp. Physiol.
Subjective social status, objective socioeconomic status, and cardiovascular risk in women
Health Psychol.
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