Five studies, checked and sourced
Peer-reviewed only — no preprints, no press releases. Each entry links directly to the paper on PubMed. Not medical advice: these are factual summaries of what a study found, not a recommendation for what you should do.
Your fitness level predicts survival better than almost anything else doctors measure
Tracking 122,007 adults referred for treadmill testing at the Cleveland Clinic, researchers found the least fit had a death rate on par with major chronic diseases — while the fittest kept seeing benefits with no upper limit.
- Study
- Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing
- Journal
- JAMA Network Open, 19 Oct 2018
- Design
- Retrospective cohort, 122,007 adults, Cleveland Clinic exercise-testing database (1991–2014)
- Authors
- Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W
A consistent bedtime may matter more than hitting 8 hours
Tracking sleep patterns in 60,977 UK adults over 7 years, researchers found how regular your sleep schedule is predicted death risk more strongly than how many hours you actually slept.
- Study
- Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study
- Journal
- Sleep, Jan 2024 (Vol 47, Issue 1, zsad253)
- Design
- Prospective cohort, 60,977 adults with valid actigraphy data, UK Biobank (1,859 deaths over follow-up)
- Authors
- Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK
Eating in an 8-hour window didn't beat plain calorie counting
In a year-long trial of 139 adults with obesity, restricting eating to 8am–4pm plus calorie restriction produced statistically similar weight loss, waist circumference and blood-marker results to calorie restriction alone.
- Study
- Calorie Restriction with or without Time-Restricted Eating in Weight Loss
- Journal
- New England Journal of Medicine, 21 Apr 2022 (Vol 386, No 16)
- Design
- Randomised controlled trial, 139 adults with obesity, 12 months, Guangzhou, China
- Authors
- Liu D, Huang Y, Huang C, Yang S, Wei X, Zhang P, et al.
Creatine helps older adults hold onto muscle — but only alongside training, not instead of it
Pooling 11 randomised trials in adults 60+, creatine added a modest but real strength benefit on top of resistance training. The effect size was small — training was still doing most of the work.
- Study
- Effects of resistance training combined with creatine supplementation on muscle strength, physical function, and muscle mass in older adults: a systematic review and three-level meta-analysis
- Journal
- Frontiers in Nutrition, 2026 (Vol 13)
- Design
- Systematic review & three-level meta-analysis, 11 RCTs, adults 60+ (effect size g = 0.31 for strength vs. resistance training alone)
Clearing "zombie cells" extended survival in aged mice — human evidence is still early
A two-drug combination that clears senescent ("zombie") cells improved physical function and extended post-treatment survival by 36% in naturally aged mice. It's a mouse study — nothing yet shows the same longevity effect in people.
- Study
- Senolytics improve physical function and increase lifespan in old age
- Journal
- Nature Medicine, 1 Aug 2018 (Vol 24, pages 1246–1256)
- Design
- Preclinical, naturally aged and senescent-cell-transplanted mice, Mayo Clinic — not a human trial
- Authors
- Xu M, Pirtskhalava T, Farr JN, Weigand BM, Palmer AK, Weivoda MM, et al.