Study archive · page 33

Pooling 162 randomised trials with 10,475 adults aged 18 to 81.6 years, exercise produced small to moderate improvements in bone mineral density at five of six skeletal sites, including the femoral neck (g 0.28) and lumbar spine (g 0.22). The authors stress that rankings of which exercise type wins, and the suggested dose peak near 1100 MET-min/week for lumbar spine, are exploratory rather than prescriptions.

⚠What it shows: The headline effect is solid, the fine detail is not: results pooled from 162 randomised trials in 10,475 adults, with confidence ranging from high at the femoral neck down to very low at the total hip. The comparisons between exercise types were imprecise, the studies disagreed with each other, and the dose figures shifted depending on where the model's edges were drawn.Review · Bone

Elastic band training improved muscle strength and functional performance compared with no exercise in healthy adults, according to a review pooling five trials. Against other resistance training methods, bands produced similar strength gains but were inferior for functional performance.

⚠What it shows: Useful but thin: only five trials of healthy adults made the cut in this sweep of the evidence, three of them high quality. Bands matched other resistance methods for strength but came out behind them on functional performance, so this is a green light for strength specifically.Meta-analysis · J Phys Act Health

In adults aged 60 or older, resistance exercise significantly improved muscle-specific strength, the force produced per unit of muscle mass, while nutritional supplements, aerobic exercise and combined approaches showed no significant benefit across 41 pooled trials with 3,141 participants.

⚠What it shows: Strong for lifting, open for everything else: results pooled from 41 trials covering 3,141 adults aged 60 and over, though the trials trained and tested people in very different ways. The null results for supplements and aerobic work mean unproven rather than disproven.Review · Ageing Res Rev

Strength training improves the nervous system's ability to switch muscle on fully in older adults, with voluntary activation rising by 8.8% in the calf muscles and 1.8% in the knee extensors across pooled trials. Gains were largest in people who started with the poorest activation.

⚠What it shows: Solid but narrow: results pooled from 17 studies of lower-body training in older adults, and the effect on the opposing muscles that brake a movement was inconsistent, so that piece of the puzzle is still open.Meta-analysis · Exp Gerontol

Training a muscle once, twice or three or more times per week produces similar growth when total weekly volume is the same, according to a meta-analysis of 25 studies. Higher frequency only helped when it brought extra total work with it.

⚠What it shows: Strong evidence by fitness research standards: results pooled from 25 studies, the finding held for trained lifters and for upper and lower body alike. The one nuance is that frequency did help when it was not matched for total work, meaning extra sessions mostly matter as a vehicle for extra volume.Meta-analysis · J Sports Sci

Higher-volume resistance training beat lower volumes for building both upper and lower body strength in adults aged 60 to 83, in a meta-analysis of 31 studies with 1,744 participants. The advantage was most pronounced after 12 weeks of training.

⚠What it shows: A consistent pattern rather than a precise prescription: results pooled from 31 studies of 1,744 independent older adults, and it does not settle exactly how many sets count as enough. The functional fitness benefit was a tendency, not a firm result.Meta-analysis · Arch Gerontol Geriatr

Pooled results from 19 randomised trials in 768 healthy adults found that taking collagen peptides daily alongside several weeks of training produced small but significant gains in fat-free mass (SMD 0.48), tendon morphology (SMD 0.67), muscle architecture (SMD 0.39) and recovery of reactive strength 48 hours after muscle-damaging exercise (SMD 0.43). Maximal strength shifted least of all, at SMD 0.19.

⚠What it shows: Decent evidence for a supplement, with sensible limits: results pooled from 19 randomised trials in 768 healthy adults who supplemented for at least eight weeks while training. The authors rated their own confidence as moderate for body composition, low for most outcomes and very low for the tendon measurements, so the size of these effects could still move.Meta-analysis · Sports Med

Pooled results from 59 randomised trials with 3802 participants found green tea extract produced significant reductions in body mass, BMI and body fat percentage, alongside lower malondialdehyde and higher adiponectin and total antioxidant capacity. Fat mass, leptin and ghrelin did not change, and certainty across outcomes ranged from low to high.

⚠What it shows: Broad but uneven: results pooled from 59 randomised trials in 3802 participants, with the authors' confidence ranging from low all the way to high depending on the outcome. The reductions were statistically significant rather than large, and fat mass itself did not move.Meta-analysis · Br J Nutr

Pooled results from six randomised trials in 476 adults found gum arabic supplementation modestly reduced weight and BMI (an average BMI drop of 0.38) and lowered fasting blood glucose, though the glucose results varied widely between studies.

⚠What it shows: Early and shaky: just six trials with 476 adults in total, follow-up periods were short, and the blood sugar results disagreed sharply between studies. The weight and BMI changes were consistent across trials but small.Review · J Diabetes Metab Disord

A systematic review of trials published between 2011 and 2024 finds that leucine-enriched whey protein combined with resistance training improves lean muscle mass, strength and physical performance in older adults with sarcopenia. Optimal dosing and long-term sustainability remain open questions.

⚠What it shows: Encouraging but imprecise: a sweep of all the studies on this from 2011 to 2024 points the same way, but the review reports no pooled numbers, and the authors themselves flag that ideal doses and long-term effects are still unknown.Systematic review · J Cachexia Sarcopenia Muscle

In a systematic review of 16 controlled trials in adult men, N-acetylcysteine (NAC) supplementation improved exercise performance, antioxidant capacity and glutathione status with no serious side effects reported, but showed no clear benefit for blood markers, inflammation or measures of muscle behaviour.

⚠What it shows: Promising but far from settled: a sweep of all the studies turned up 16 controlled trials in adult men, most reporting benefits, but the results were never pooled into a single number and the authors themselves call for more research. Women were not studied, so nothing here applies to them yet.Systematic review · Nutrients

Pooled results from 10 randomised trials covering 400 adults with overweight or obesity found exercise training improved flow-mediated dilation, a marker of blood vessel function; the benefit was clear for aerobic training while resistance training fell just short of statistical significance.

⚠What it shows: Encouraging but thin: results pooled from 10 trials covering just 400 adults, and the quality checks raised some concerns, so the authors themselves urge caution. Lifting fell just short of a clear effect, which leaves its role unresolved rather than disproven.Meta-analysis · Sci Rep

Pooling 17 trials in 576 healthy women, exercise produced modest improvements in blood lipids: total cholesterol fell by 5.77 mg/dL, triglycerides by 5.60 mg/dL, and HDL cholesterol rose by 4.49 mg/dL. Combined training was most effective for triglycerides and total cholesterol, while aerobic exercise significantly raised HDL.

⚠What it shows: A real but small effect: results pooled from 10 articles covering 17 trials with 576 healthy women in total. The trials tested different types and intensities of exercise, so this cannot tell you how much or how hard to train to get the same shift.Meta-analysis · J Physiol Biochem

Brief exercise snacks significantly improved VO2max and peak power output in pooled data from 21 trials of 921 adults, but the VO2max gains appeared only in groups with average ages under 50, body fat percentage nudged upwards on low-certainty evidence, and blood lipids did not change.

⚠What it shows: Reasonably solid for fitness: results pooled from 21 trials in 921 adults, with moderate confidence in the VO2max gains but only low confidence in the odd rise in body fat. The age split compares whole studies rather than individuals, so the authors themselves say it needs confirming.Review · J Nutr Health Aging

Exercise improved self-reported erectile function in men diagnosed with erectile dysfunction, with a pooled gain of 3.85 points on the International Index of Erectile Function across 7 trials and 478 participants. Aerobic exercise at moderate to vigorous intensity showed the clearest benefit.

⚠What it shows: Worth taking seriously: results pooled from 7 trials in 478 men with diagnosed erectile dysfunction, and the benefit held across programmes lasting 8 weeks to 2 years. Nobody could be blinded to whether they were exercising and the score is self-reported, which can flatter the result.Meta-analysis · Br J Sports Med

Vigorous aerobic exercise and HIIT ranked most likely to be the best interventions for reducing visceral fat in a pooled comparison of 84 randomised trials covering 4836 adults with overweight or obesity. Resistance training ranked least effective and did not reduce visceral fat in women or in people with body fat of 40% or more.

⚠What it shows: About as broad as exercise evidence gets: 84 trials and 4836 adults with overweight or obesity, pooled and ranked against each other. The rankings reflect the probability of being best rather than certainty, and why lifting failed to shift visceral fat in women needs more study.Meta-analysis · Obes Rev

The triglyceride-glucose index, a cheap marker built from routine blood tests, was linked with roughly double the cardiovascular risk in a Chinese cohort, yet adding it to the Framingham Risk Score barely improved prediction, and pooled results across five cohorts found a negligible gain.

⚠What it shows: A useful corrective rather than a final word: one Chinese study following adults aged 45 to 80, plus results pooled from five similar studies, none of which tested the marker in a trial. The authors themselves rated the certainty on the prediction question as very low.Study · Front Cardiovasc Med

Across 97 randomised trials in adults with overweight and obesity, adding exercise to a low-calorie diet improved blood glucose, insulin, insulin resistance, triglycerides, HDL cholesterol and blood pressure more than diet alone, with the benefits tied mainly to aerobic exercise, especially supervised high-intensity cycling, rather than resistance training.

⚠What it shows: Broad but not bulletproof: results pooled from 97 trials in adults with overweight or obesity, yet the authors rate the evidence as only moderate to low certainty. The clearest gains came from supervised high-intensity programmes, so casual unsupervised exercise may not deliver the same result.Meta-analysis · Nutr Rev

Exercise significantly increased bone mineral density at the lumbar spine and femoral neck in older adults, in a meta-analysis of 19 randomised trials with 1577 participants. Programmes combining impact activity with resistance training loading, and odd-impact protocols, were the effective types; low-impact and resistance-only exercise showed no significant change.

⚠What it shows: Strong by exercise-science standards: 19 trials with 1577 older adults, moderate to high quality, and no sign that negative results were left unpublished. The bone gains were small and results for some exercise types disagreed with each other, so the ideal programme is not yet settled.Meta-analysis · Age (Dordr)

Exercise brings small but significant reductions in pain and disability for people with chronic low back pain, and of the eight programme and trial features examined, only dosage, the total amount of exercise delivered, was linked to how well it worked.

⚠What it shows: Solid footing: this pooled the randomised trials of exercise for chronic low back pain and the benefit, though small, held up. It compared whole studies rather than individual patients, so it cannot say which kind of person benefits most, and the search only ran to 2008.Meta-analysis · Phys Ther

Diets rich in beta-glucans, the fibre found in oats and barley, lowered systolic blood pressure by 2.9 mmHg and diastolic by 1.5 mmHg for a median 4 g increase, in pooled trials of healthy adults; higher fibre intake overall produced no significant reduction.

⚠What it shows: Solid for the oats finding: results pooled from trials of healthy adults, 18 studies in the final numbers, all lasting at least six weeks. Fibre overall showed no clear effect on blood pressure, so the case here is for beta-glucan sources specifically, not fibre in general.Meta-analysis · J Hypertens

Pooled results from 10 randomised trials in 2134 adults with insomnia or poor sleep found cannabinoids reduced insomnia severity and improved sleep quality scores, increased total sleep time by 33.99 min, lifted sleep efficiency by 4.31% and modestly cut time to fall asleep by 12.0 min. Side effects, mostly mild dizziness and dry mouth, were roughly four times more frequent than with comparators, with no serious harms recorded.

⚠What it shows: Encouraging but not the last word: results pooled from 10 randomised trials in 2134 adults, comparing cannabinoids against placebo or melatonin. The trials were mostly short, so the right dose and whether the benefit lasts are both unresolved, and mild dizziness and dry mouth were clearly more common.Review · Sleep Med

Resistance training was associated with 21% lower all-cause mortality on its own, and 40% lower when combined with aerobic exercise, in a meta-analysis of 11 studies totalling 370,256 people followed for an average of 8.85 years.

⚠What it shows: Compelling but not causal: 10 of the 11 pooled studies followed people rather than assigning them to lift, so healthier people may simply be more likely to train. The link with cancer deaths was not significant and cardiovascular mortality was only borderline.Meta-analysis · Eur J Prev Cardiol

Oral hydrolysed collagen taken for 90 days reduced wrinkles and improved skin hydration and elasticity compared with placebo in a meta-analysis of 19 randomised, double-blind trials with 1,125 participants aged 20 to 70, 95% of them women.

⚠What it shows: Stronger than most supplement claims: results pooled from 19 placebo-controlled trials in 1,125 people, where neither participants nor researchers knew who got the real thing. Almost all participants were women aged 20 to 70, so the evidence says little about men.Meta-analysis · Int J Dermatol