In summary: insufficient or irregular sleep is associated, in studies, with some metabolic and cardiovascular outcomes. This does not prove that sleeping more, by itself, prevents diabetes, promotes weight loss, or prolongs life. Sleep duration, regularity, quality, and possible disorders need to be considered together.
Discussing sleep and metabolism is important because sleep plays a role in the daily organization of biological processes and behaviors that influence health. Research also investigates relationships between sleep habits, healthy aging, and mortality. But it is essential to distinguish association from causation: these studies do not justify promises of longevity or replace individual assessment.
How many hours of sleep are recommended?
A joint consensus from the American Academy of Sleep Medicine and the Sleep Research Society recommends that adults aged 18 to 60 sleep at least seven hours per night on a regular basis to promote health. This recommendation does not mean that seven hours are enough for everyone, or that there is a magic number valid for any age or situation. Individual needs vary, and the consensus itself recognizes that sleeping more may be appropriate in some contexts.1
In addition to duration, sleep health involves quality, timing, regularity, and the presence or absence of disorders. Therefore, spending many hours in bed does not guarantee restorative sleep. Persistent insomnia, frequent awakenings, loud snoring with pauses in breathing, or daytime sleepiness may require clinical investigation.
What does the science show about sleep and metabolism?
Observational studies link short sleep, poor-quality sleep, and highly variable sleep schedules to less favorable metabolic indicators. Hypotheses under investigation include changes in appetite, food intake, physical activity, and alignment between the biological clock and daily routines. These factors influence one another; an association observed in a group does not determine what will happen to a specific person.
A randomized clinical trial helps illustrate what can be concluded—and what cannot. The study included 80 adults aged 21 to 40 with overweight who habitually slept less than 6.5 hours. Over two weeks, the group advised to increase their sleep opportunity slept, on average, about 1.2 hours more per night and showed an average reduction of 270 kilocalories per day in energy intake compared with the control group.2
The finding is relevant, but has limitations: the study was short, included a selected group, and does not demonstrate that sleep extension alone treats obesity or produces lasting weight loss. Adequate sleep can be part of healthy habits, but does not replace individualized assessment and care.
A systematic review and meta-analysis published in 2025 found a U-shaped association between sleep duration and the observed risk of type 2 diabetes, with lower estimates in ranges close to 7 to 8 hours. The included studies were observational and mostly based on participants’ reports of their own sleep. The authors highlight the possibility of residual confounding; therefore, the finding does not prove that a specific duration causes or prevents diabetes.3
Sleep regularity and the biological clock
Regularity means keeping bedtimes and wake-up times relatively consistent from one day to the next. This does not require everyone to follow the same routine: shift work, family responsibilities, clinical conditions, and other factors can affect schedules. Nevertheless, large, recurring variations between weekdays and weekends are a topic of research on circadian rhythms and cardiometabolic health.
In a UK Biobank cohort, researchers analyzed sleep measurements obtained using wrist accelerometers in 60,977 participants. Greater regularity was associated with lower mortality during follow-up, which extended to 7.8 years. The study is observational: one week of monitoring is only a snapshot of habitual sleep, and the association does not demonstrate that making schedules more regular, on its own, prolongs life.4
A scientific review from the American Heart Association, published in 2025, brought together evidence on sleep irregularity, circadian misalignment, and cardiometabolic risk. The authors note that standardized measures and intervention studies capable of better clarifying what changes when regularity is modified in real life are still lacking.5
Sleep and healthy aging: what should not be promised
Healthy aging depends on many factors, including health conditions, physical activity, diet, environment, social relationships, and access to care. The sleep literature adds an important dimension to this discussion, but does not demonstrate that a specific sleep routine, supplement, or product increases someone’s longevity.
Consumer watches and apps can help track trends, but do not replace clinical assessment or validated diagnostic tests. The American Academy of Sleep Medicine states that these devices should not be used on their own to diagnose sleep disorders.6
General habits that may help organize sleep
As a starting point, it may be useful to set aside enough time to sleep and maintain relatively predictable wake-up times, within the possibilities of each routine. Recording sleep times, awakenings, and daytime sleepiness for a few days may help describe the problem during a consultation.
Seek professional assessment if you have persistent difficulty sleeping, frequent snoring with observed pauses in breathing, nighttime choking, or daytime sleepiness that interferes with activities. Learn more about persistent insomnia and obstructive sleep apnea. The guidance on this page is educational and does not replace an individual consultation, diagnosis, or treatment.
Frequently asked questions
Is seven hours of sleep enough for every adult?
Not necessarily. The AASM/SRS consensus recommends at least seven hours regularly for adults aged 18 to 60, but individual needs vary. Quality, regularity, and symptoms also matter.1
Does sleeping more help with weight loss?
A short trial found a reduction in energy intake after sleep extension in a specific group of adults with overweight and habitually short sleep. This does not demonstrate that sleeping more is a stand-alone treatment for obesity or that the effect is maintained over the long term.2
Are regular sleep schedules proven to increase longevity?
There is no proof that making schedules more regular, by itself, prolongs life. Cohort studies have found associations between regularity and mortality, but do not establish causality or allow an individual’s outcome to be predicted.4
Scientific references
- Watson NF et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. SLEEP. 2015;38(6):843–844. Full text.
- Tasali E et al. Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings: a randomized clinical trial. JAMA Internal Medicine. 2022;182(4):365–374. Study text.
- Liu H et al. Sleep features and the risk of type 2 diabetes mellitus: a systematic review and meta-analysis. Annals of Medicine. 2025;57(1):2447422. Full text.
- Windred DP et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. SLEEP. 2024;47(1):zsad253. Full text.
- Huang T. Sleep irregularity, circadian disruption, and cardiometabolic disease risk. Circulation Research. 2025;137(5):709–726. Abstract and references.
- American Academy of Sleep Medicine. Consumer sleep technology is no substitute for medical evaluation. 2018. Official position statement.
About the author
Dr. Flávio H. Barbosa — CRM-DF 14908 · RQE 12569 in Sleep Medicine. To learn about his work and content related to the specialty, visit the Sleep Medicine page.