The Link Between Sleep and Obesity – A Review of the Latest Research

Global rates of obesity and type 2 diabetes mellitus have been rising concurrently with reduced sleep duration. Epidemiological cohort studies have established an association between short sleep duration and increased obesity, but its exact mechanisms remain unknown.

This review presents a literature assessment pertaining to sleep and obesity. A keyword/reference search was performed in January 2021 on MEDLINE/PubMed, EMBASE/Ovid, PsycINFO/EBSCO, The Cochrane Library and SciELO/Web of Science databases.

1. Sleep Deprivation Increases Food Intake

Adequate sleep is crucial to your mood, memory and performance at work or school. An inadequate amount of restful zzzs may also impact heart and brain health, sex drive and your ability to cope with stress effectively. A lack of quality rest may also increase weight and obesity – leading to serious health complications down the line.

Previous behavioral studies have reported increased caloric intake and altered food choices following sleep loss under free-living conditions1. These observations could be due to sleep-dependent peripheral body changes that lead to cravings for unhealthy foods, or central nervous system dysfunction. In this study, we employed human fMRI to investigate how sleep deprivation affects neural mechanisms governing appetite-inducing food desirability and choice. Sleep deprivation was found to reduce recruitment of key cortical regions involved in food stimulus evaluation and increase subcortical amygdala (but not ventral striatal) reactivity; leading to significantly greater desirability ratings for high-calorie foods than under normal sleep conditions.

2. Short Sleep Duration Increases Obesity Risk

Studies with both children and adults have demonstrated the relationship between short sleep duration and increased obesity risk and dysfunctional eating behaviors, reduced physical activity, and metabolic changes (e.g. increased levels of ghrelin, decreased leptin production, and diminished insulin sensitivity). This could explain why short sleeping duration increases obesity risk.

Cross-sectional studies have revealed that those reporting sleeping less than the recommended amount are more likely to be overweight or obese compared to those getting 7 hours of restful sleep on a consistent basis. Other factors affecting both sleeping habits and weight, like smoking cigarettes or alcohol drinking can play a part in contributing to these results.

Studies conducted over time have also demonstrated a correlation between short sleep duration and increased future weight gain and reducing time spent sleeping as an effective strategy to combat the global obesity epidemic.

3. Sleep Deprivation Increases Weight Gain

Studies demonstrate how sleep deprivation alters levels of hormones that regulate appetite. When we’re tired, leptin levels drop off significantly while hunger spikes up with higher ghrelin levels.

Hormonal changes can contribute to overeating and weight gain. Studies have revealed that people who sleep less tend to favor more calorically dense food options like high-fat and carb snacks.

Sleep loss renders many diets that involve caloric reduction less effective, according to studies with both prospective and cross-sectional data. Short sleep duration has been shown to lead to increased energy intake from snacking on high-fat, sugary foods – creating a major obstacle in weight loss efforts and maintaining healthy bodyweight over the long-term.

4. Sleep Deprivation Increases Risk of Cardiovascular Disease

Sleep deprivation increases your risk of heart attacks and stroke, both life-threatening conditions that require immediate medical care. But even without emergency conditions present, long term sleep deprivation increases the likelihood of many health issues – from weaker immune systems, altered insulin and blood pressure levels, as well as changes to body fat storage patterns.

Studies have demonstrated that those who get less sleep are at greater risk of coronary heart disease (CAD) than those who sleep longer, possibly due to reduced levels of GABA neurotransmitter activity resulting in reduced central inhibition and an increase in sympathetic tone associated with coronary artery disease (CAD). Additionally, shorter sleep duration can decrease body’s ability to clear inflammation out of blood vessels creating an “U” shaped relationship between sleep duration and inflammation markers.

5. Sleep Deprivation Increases Risk of Diabetes

Diabetes and obesity rates coincide with declining sleep duration, according to studies which measured blood sugar levels of those sleeping for less than seven hours a night; such individuals were 40% more likely to develop diabetes than others.

Lack of sleep disrupts fat cells and increases our body’s dependency on glucose for energy, decreasing insulin’s ability to manage blood sugar levels effectively, which causes diabetic symptoms like fatigue and frequent thirst and urination.

Epidemiological cohort studies have established short sleep duration as an independent risk factor for developing diabetes; however, its exact mechanisms remain unknown and further investigation will likely shed more light on them. Gender and race/ethnic variations in short sleep patterns could also play a factor in differences in rates of prevalence for diabetes.