Lack of sleep and bulging waistlines
Obesity is one of the most critical health problems currently facing our planet. The prevalence of overweight and obesity has continued to rise in recent decades, with nearly one in five children and more than one in three adults in the U.S. now classified as obese (http://www.cdc.gov/obesity/data). The extraordinary ramifications of this epidemic on physical health, emotional wellbeing, and the economy cannot be overstated. Medical costs associated with the current obesity epidemic have been estimated to be in the hundreds of billions of dollars annually . As the population of our nation ages in the midst of a struggling economy and a healthcare system that is in flux, this upward trend must be reversed rapidly and dramatically if we are to avert catastrophic consequences. Weight gain is an astonishingly complex phenomenon that often defies simple attempts to curtail its advance. Simplistic solutions are unlikely to prove successful in preventing or reversing obesity, but even the most complex approaches are likely to fail if they do not incorporate core elements of human functioning that contribute to weight gain. Recent research suggests that one of these core elements is adequate sleep.
While the causal links have yet to be established, it is obvious that the expanding girth of the average waistline has coincided closely with the insidious decline in average sleep time over the past century . Recent data suggest that most healthy adults in the U.S. sleep less than 7 hours per night , and nearly one-in-three workers gets 6 or less hours per night , an amount nearly 2 to 3 hours less than was common in the early 20th century . The invention of electric lighting, television, computers, the internet, mobile communication devices, and the changes in lifestyle and vocational expectations that have accompanied these advances, have all undoubtedlycontributed to the decline in nightly sleep. Cross sectional data suggest that reduced sleep duration is associated with a number of health problems including obesity . Longitudinal and prospective data bolster this argument and suggest that individuals who self-report shorter sleep duration at one point in time show a greater risk of gaining excess weight in the ensuing years [5,7,8].
Clearly, people who sleep less appear to be at greater longterm risk for overweight and obesity, but the precise nature of these relationships still remains uncertain and more research needs to be directed towards elucidating these factors. It is known that experimental restriction of sleep leads to alterations in metabolic hormones, including reduced leptin and increased ghrelin levels, which likely contribute to feelings of hunger and increased food consumption during periods of extended wakefulness [9,10]. All things being equal, a sleep-deprived person will consume more food, particularly sweet, high carbohydrate snacks or desserts with low nutrition density compared to when well rested. Additionally, because lack of sleep leads to fatigue and reduced energy, sleepdeprived individuals tend to curtail their physical activity and therefore, expend fewer calories despite a longer time spent awake . While the basic metabolic changes that occur during sleep loss may play a major role in the obesity epidemic, recent functional neuroimaging findings also raise additional concerns about the subtle effects that sleep deprivation can have on cognitive control systems within the brain. Sleep deprivation leads to altered brain functioning within executive control networks important for regulating emotions and controlling behavior . Sleep deprivation is associated with reduced inhibitory capacity , greater risk-taking , and cognitive biases that tend to favor the influences of rewards over punishments . Now, emerging neuroimaging evidence suggests these same cognitive systems may also be altered by sleep loss to affect emotional and perhaps even self-regulatory responses to food stimuli [16,17]. Could sleep loss also be subtly affecting our ability to say no to unhealthy food choices, make good decisions regarding portion sizes, and put down our forks when we have eaten a reasonable amount? How much sleep loss leads to weight gain? Are there individual differences in the extent to which sleep restriction affects appetite or food consumption? Can counter measures such as caffeine or light exposure affect food intake in sleep-restricted individuals? Perhaps most urgently, it will be critical to understand how reduced sleep is affecting the growing problem of obesity among adolescents, a population that is particularly vulnerable to sleep loss, poor dietary choices, targeted advertising, peer pressure, and the use of caffeinated energy drinks. These unanswered questions are ripe for research.
The epidemic of obesity has never been more pressing. The longterm implications of this epidemic on the physical and economic health of our nation and the world are potentially staggering. While the problem is multifaceted, sleep medicine is uniquely poised to address a clear and modifiable aspect of behavior that appears to play a major role in the potential for long-term weight gain. When combined with careful calorie control and physical activity, sleep regulation may be the third controllable piece to the puzzle. Continued research into this problem is vital, but the existing evidence is already strong enough to demand greater implementation of sleep oriented education and clinical sleep interventions to minimize the effects of sleep loss on weight gain.
- Finkelstein EA, Trogdon JG, Cohen JW, Dietz W (2009) Annual medical spending attributable to obesity: payer-and service-specific estimates. Health Aff (Millwood) 28: w822-w831.
- Mavanji V, Billington CJ, Kotz CM, Teske JA (2012) Sleep and obesity: a focus on animal models. Neurosci Biobehav Rev 36: 1015-1029.
- Adult Sleep Habits and Styles (2005) National Sleep Foudation.
- Centers for Disease Control and Prevention (CDC) (2012) Short sleep duration among workers–United States, 2010. MMWR Morb Mortal Wkly Rep 61: 281-285.
- Patel SR (2009) Reduced sleep as an obesity risk factor. Obes Rev 10: 61-68.
- Patel SR, Blackwell T, Redline S, Ancoli-Israel S, Cauley JA, et al. (2008) The association between sleep duration and obesity in older adults. Int J Obes (Lond) 32: 1825-1834.
- Gangwisch JE, Malaspina D, Boden-Albala B, Heymsfield SB (2005) Inadequate sleep as a risk factor for obesity: analyses of the NHANES I. Sleep 28: 1289-1296.
- Hasler G, Buysse DJ, Klaghofer R, Gamma A, Ajdacic V (2004) The association between short sleep duration and obesity in young adults: a 13-year prospective study. Sleep 27: 661-666.
- Brondel L, Romer MA, Nougues PM, Touyarou P, Davenne D (2010) Acute partial sleep deprivation increases food intake in healthy men. Am J Clin Nutr 91: 1550-1559.
- Morselli L, Leproult R, Balbo M, Spiegel K (2010) Role of sleep duration in the regulation of glucose metabolism and appetite. Best Pract Res Clin Endocrinol Metab 24: 687-702.
- Benedict C, Hallschmid M, Lassen A, Mahnke C, Schultes B (2011) Acute sleep deprivation reduces energy expenditure in healthy men. Am J Clin Nutr 93: 1229-1236.
- Killgore WD (2010) Effects of sleep deprivation on cognition. Prog Brain Res 185: 105-129.
- Drummond SP, Paulus MP, Tapert SF (2006) Effects of two nights sleep deprivation and two nights recovery sleep on response inhibition. J Sleep Res 15: 261-265.
- Killgore WD, Grugle NL, Balkin TJ (2012) Gambling when sleep deprived: don’t bet on stimulants. Chronobiol Int 29: 43-54.
- Venkatraman V, Huettel SA, Chuah LY, Payne JW, Chee MW (2011) Sleep deprivation biases the neural mechanisms underlying economic preferences. J Neurosci 31: 3712-3718.
- Benedict C, Brooks SJ, O’Daly OG, Almon MS, Morell A, et al. (2012) Acute sleep deprivation enhances the brain’s response to hedonic food stimuli: an fMRI study. J Clin Endocrinol Metab 97: E443-E447.
- St-Onge MP, McReynolds A, Trivedi ZB, Roberts AL, Sy M, et al. (2012) Sleep restriction leads to increased activation of brain regions sensitive to food stimuli. Am J Clin Nutr 95: 818-8 24.