Four ways lack of sleep can help make you obese
Research shows getting too little sleep can have a raft of negative consequences, from overeating to making poor decisions
We all know how hard it is to get through a work day after a bad night's slumber, but there's a growing pool of evidence that links poor sleep quantity and quality to increased food intake in both adults and children.
In a new paper published in the Journal of Health Psychology, researchers from the University of Nebraska-Lincoln reviewed published studies and conclude that sleep patterns heavily alter and influence the biological, emotional, cognitive, behavioural and environmental factors that drive food intake.
These factors may also influence each other, further compounding the effect of disrupted sleep on increased food consumption.
Specific emphasis is placed on environmental factors such as high-stress environments, which the researchers say put some individuals at "dual risk" for both disrupted sleep patterns and excessive eating.
But it's not just how long you sleep; the time you hit the sack and the variability of sleep patterns affect food intake, too.
Seasonal variations in light and temperature may affect sleep patterns, and, therefore, food intake. Research shows poorer sleep and greater food intake in the autumn and winter.
Societal issues may also play a role, the researchers say. The increase of "24-hour societies" due to greater economic and social demands, results in shift work outside normal office hours. Shift work interferes with circadian rhythms, thus disrupting sleep. Subsequently, this may alter food intake, which could help explain greater rates of obesity and diet-related conditions in shift workers.
The same goes for early school starting times: children in schools that start only 30 to 50 minutes before comparison schools have shorter sleep durations and increased daytime sleepiness, according to studies.
"It is well recognised that food intake is implicated in many chronic health issues, including obesity, diabetes and heart disease, and diet is often a target of treatment to prevent the onset of these conditions," say the researchers Alyssa Lundahl and Timothy D. Nelson.
"Understanding the mechanisms linking disrupted sleep patterns to increased food intake is important for informing both prevention and treatment interventions for chronic health conditions."
Researcher say these are four reasons why the less you sleep, the more you eat.
Lack of sleep makes your appetite hormones go haywire
Disrupted sleep patterns result in a hormonal state that makes you tend to overeat. Studies show that after sleep restriction, adults increase their daily energy intake by 20 per cent, yet their perceived pleasantness of foods or desire to eat is unchanged. There's also evidence that people increase portion sizes after sleep deprivation, irrespective of food type.
Two hormones - leptin and ghrelin - are widely thought to be the culprits. Leptin sends satiating signals to the appetite control centres of the brain, while ghrelin sends signals from the stomach to the brain that trigger an increase in appetite.
Although other hormones such as cortisol, insulin and glucocorticoids are also involved, research indicates that the ratio of leptin to ghrelin accounts for nearly 70 per cent of the variance in increase in hunger after sleep restriction.
Most studies indicate disrupted sleep increases ghrelin levels, hence appetite, while lack of sleep lowers leptin levels, resulting in a misperception of insufficient caloric intake Decreased leptin levels are also linked with an increased appetite for sweet, salty and starchy foods.
"The biological drive to eat after sleep disruption may increase as the body attempts to compensate for the nocturnal energy deficit resulting from increased wakefulness and the associated increase in energy expenditure," the researchers say.
Lack of sleep puts you in a negative mood, so you turn to food to feel better
Sleep plays an integral role in emotional regulation, modulating affective neural systems and reprocessing recent emotional experiences. Disrupted sleep patterns lead a person to view "the glass half empty" and experience heightened emotional distress.
Negative moods are associated with greater food consumption in both adults and children. Sweet or energy-dense foods are especially pleasing, as they effect the opioidergic, dopaminergic and serotonergic systems that relate to pain, reward, pleasure and happiness, thereby improving the mood and mitigating effects of stress.
Lack of sleep affects your ability to get things done - including eating right
Disrupted sleep patterns are associated with impairments in cognitive functioning, in particular executive function, which in turn has shown in studies to increase food intake in both adults and children.
Executive function is like the CEO of the brain. It plays a part in organising healthy eating goals and planning eating behaviour. It's also important for engaging in mindful eating.
Among adults, studies have shown that weaker executive control is related to a greater consumption of snacks and high-fat foods and fewer fruits and vegetables than one intends to consume. Among children, it's related to a greater consumption of high-calorie snacks, and an increase in eating in the absence of hunger.
Neural imaging also shows disrupted sleep affects reward processing in the brain, amplifying brain reactivity to pleasurable stimuli and can lead to increased reward-seeking behaviour, such as eating.
People with a higher sensitivity to reward are more likely to have stronger food cravings and a greater body mass index than those with less sensitivity to reward, research shows. They also tend to prefer food high in sugar and fat, and have greater neural activation in response to images of food.
Lack of sleep makes you more impulsive in your food choices
Research with adults suggests sleep deprivation results in greater difficulty withholding inappropriate responses and reacting more quickly - albeit incorrectly - to behavioural tasks.
These behavioural deficits may be related to greater susceptibility for increased food consumption.
Impulse control plays an important role in inhibiting appetitive thoughts and behaviour when one is confronted with a situation in which the consumption of excess food is promoted.