Sauna for overweight and obesity
Evidence review
Overview
Passive heat alone has not produced weight loss in people with overweight or obesity. In a randomized trial of 66 overweight Japanese adults, hot bathing alone produced no significant improvements, while a program combining hot bathing with exercise and diet reduced weight and waist circumference more than the other arms. Small studies report lower fasting glucose and insulin after 10 hot-water immersions, better lipids and vascular compliance (but not fitness) after 12 weeks of half-body bathing compared with no treatment in obese men, improved quality-of-life scores after 8 dry-sauna sessions without change in body composition, and acute reductions in blood pressure and increases in limb and skin blood flow after one hot-water immersion. Weight lost during a sauna session is mainly fluid.
Key findings
- RCT, 66 overweight adults, 3 months: hot bathing alone produced no significant improvements; exercise + diet + hot bathing reduced weight, abdominal circumference, BMI and body fat vs the other groups (Sakurai 2013).
- Controlled trial, BMI 31: 10 hot-water immersions (102 F, 1 h) over 2 weeks lowered fasting glucose 4.44 to 3.98 mmol/L (80 to 72 mg/dL) and insulin 68.1 to 55.0 pmol/L vs controls (P=0.04 each) (Hoekstra 2018).
- Controlled trial, 30 obese middle-aged men, 12 weeks: half-body bathing improved triglyceride, LDL-C, HDL-C and vascular compliance vs no treatment but not fitness; aerobic exercise improved more measures (Kim 2012, Korea).
- Uncontrolled, n=38, mean BMI 28.5: 8 dry-sauna sessions (194 F, 15 min) improved EQ-5D index 0.83 to 0.89 and EQ-VAS 79.0 to 91.1; BMI, blood pressure and body composition unchanged (Choi 2020).
- Crossover, n=25, BMI ~29: one 30-min hot-water immersion at 104 F lowered systolic BP by 5.7 vs +0.6 mmHg after cycling (p=0.019) and diastolic BP by 9.2 vs 1.5 mmHg (p=0.001) (Locatelli 2026).
- Systematic review (10 studies): passive hydrothermal interventions showed variable anthropometric and lipid findings; certainty of evidence low to low-to-moderate (2026).
Every study we reviewed
6 mixed results · 4 found benefit · 1 found no effect
Each study was checked on PubMed. The colored edge shows the direction of the result. The research library lists 34 studies on obesity, across all heat and cold therapies, including case reports and older work not graded here.
Effects of a comprehensive intervention program, including hot bathing, on overweight adults: a randomized controlled trial.
Sakurai R et al. Geriatr Gerontol Int. 2013. PubMed 23095006 · DOI · Free full text
- Who
- Community-dwelling overweight Japanese adults (mean age 61.6, 77% women)
- What
- Hot bathing at a hot-bath facility alone, or combined with exercise and diet classes, vs exercise and diet alone vs control (4 arms)
- Protocol
- 2/wk · 12 wk
- Measured
- Weight, abdominal circumference, BMI, body fat, walking speed
- Result
- Exercise + diet + hot bathing reduced weight, abdominal circumference, BMI and body fat vs the other groups; hot bathing alone produced no significant improvements in any measure.
- Limitations
- Hot bathing could not be separated from exercise and diet in the effective arm; small arms; numbers not given in abstract.
Acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults.
Hoekstra SP et al. J Appl Physiol (1985). 2018. PubMed 30335579 · DOI · Free full text
- Who
- Sedentary overweight or obese men (BMI 31.0 intervention; 30.0 controls)
- What
- Hot-water immersion, 10 sessions over 2 weeks vs non-immersed BMI-matched controls (after an acute session vs ambient rest)
- Protocol
- 102 (water) °F · 60 min · 5/wk · 2 wk
- Measured
- IL-6, nitrite, HSP72, fasting glucose and insulin
- Result
- After 10 sessions vs controls: fasting glucose 4.44 to 3.98 mmol/L (P=0.04), insulin 68.1 to 55.0 pmol/L (P=0.04), eHsp72 -17% (P=0.03). A single session raised IL-6 (1.37 to 2.51 pg/mL) and nitrite acutely.
- Limitations
- Non-randomized; very small; 2 weeks; men only; surrogate outcomes.
Repeated Dry Sauna Therapy Improves Quality of Life in Obese Korean People.
Choi HS et al. Korean J Fam Med. 2020. PubMed 32434303 · DOI · Free full text
- Who
- Korean adults with BMI >=25 (mean 28.5, mean age 62, 84% women)
- What
- Dry sauna, twice daily for 4 consecutive days (8 sessions)
- Protocol
- 194 °F · 15 min · 8 sessions in 4 days/wk
- Measured
- EQ-5D-5L index and EQ-VAS; BMI, blood pressure, heart rate, body composition
- Result
- EQ-5D index 0.83 to 0.89 and EQ-VAS 79.0 to 91.1 (significant); no significant change in BMI, blood pressure, heart rate or body composition; no adverse events.
- Limitations
- Uncontrolled; very short; quality of life measured 2 days after the last session.
Changes in cardiac function before and after hot water immersion and endurance exercise in middle-aged individuals with overweight or obesity.
Locatelli JC et al. Eur J Appl Physiol. 2026. PubMed 42762318 · DOI · Free full text
- Who
- Middle-aged adults with overweight or obesity (15 women, 10 men)
- What
- Single hot-water immersion to the sternum vs 30 min of cycling at 60-70% max heart rate, randomized order
- Protocol
- 104 (water) °F · 30 min · single session/wk
- Measured
- Blood pressure, LV global longitudinal strain, TAPSE
- Result
- Systolic BP -5.7 vs +0.6 mmHg (p=0.019) and diastolic BP -9.2 vs -1.5 mmHg (p=0.001) after immersion vs cycling; LV GLS change -2.5% vs -0.76% (p=0.008); TAPSE +3.95 mm after immersion (p<0.001); heart rate +33 vs +25 bpm.
- Limitations
- Acute single session; surrogate outcomes; likely the same participants as Costa 2026 and Wigati 2026.
Sex differences in macrovascular responsiveness: Acute effects of hot water immersion versus aerobic exercise in overweight older adults.
Costa JG et al. Exp Physiol. 2026. PubMed 42789735 · DOI · Free full text
- Who
- Overweight older adults (BMI 29.4, age 59; 10 men, 15 women)
- What
- Single hot-water immersion vs 30 min aerobic exercise
- Protocol
- 104 (water) °F · 30 min · single session/wk
- Measured
- Core temperature, heart rate, blood pressure, brachial/femoral/carotid diameter and flow
- Result
- Systolic BP -6 vs +1 mmHg (P=0.012) and diastolic BP -10 vs -2 mmHg (P=0.001) after immersion vs exercise; larger increases in brachial diameter and brachial and femoral flow and shear rate after immersion.
- Limitations
- Acute single session; surrogate outcomes; likely overlapping participants with Locatelli 2026 and Wigati 2026.
Comparison between exercise and hot water immersion on skin microvascular responses in older adults with overweight and obesity.
Wigati KW et al. Eur J Appl Physiol. 2026. PubMed 42803957 · DOI · Free full text
- Who
- Overweight older adults (BMI 29.4, age 59; 10 men, 15 women)
- What
- Single seated hot-water immersion to the xiphoid with arms submerged vs 30 min moderate cycling, randomized
- Protocol
- 104 (water) °F · 30 min · single session/wk
- Measured
- Forearm skin microvascular diameter, velocity, flow and vessel density (optical coherence tomography)
- Result
- Greater increases after immersion than exercise (all P<0.001): flow +68.9 vs -8.3 pL/s; vessel density +14.1% vs -3.1%; larger systolic and diastolic BP reductions after immersion (P<0.01).
- Limitations
- Acute single session; surrogate outcomes; likely overlapping participants with Locatelli 2026 and Costa 2026.
Correlations between Repeated Use of Dry Sauna for 4 x 10 Minutes, Physiological Parameters, Anthropometric Features, and Body Composition in Young Sedentary and Overweight Men: Health Implications.
Podstawski R et al. Biomed Res Int. 2019. PubMed 30800676 · DOI · Free full text
- Who
- Young sedentary overweight men (mean age 20.8)
- What
- Finnish sauna, four 10-min sessions with 5-min cool-down breaks (single visit)
- Protocol
- 194-196 °F · 40 (4 x 10) min · single visit/wk
- Measured
- Heart rate, blood pressure, energy expenditure, body mass loss
- Result
- All physiological parameters rose significantly across sessions (p<0.0001); body mass fell 0.65 kg; heart rate, blood pressure and energy expenditure responses correlated with body mass, BMI and body fat.
- Limitations
- Single visit; uncontrolled; body mass loss reflects sweat; young men only.
Acute effects of exercise or sauna on appetite in obese and nonobese men.
Westerterp-Plantenga MS et al. Physiol Behav. 1997. PubMed 9383124 · DOI
- Who
- Young obese (BMI 28.5) and non-obese (BMI 22.8) men
- What
- 2 h sauna vs 2 h cycling at 60% Wmax vs 2 h rest, random order
- Protocol
- 120 min · single session/wk
- Measured
- Hunger, thirst, taste perception, energy intake, macronutrient choice
- Result
- Sauna and cycling each caused 3 +/- 0.5% body-mass loss and increased thirst and fluid intake; hunger and energy intake decreased only after cycling, not after sauna.
- Limitations
- Acute; obese and non-obese pooled in abstract; body-mass loss is fluid.
The effect of passive heating on heat shock protein 70 and interleukin-6: A possible treatment tool for metabolic diseases?
Faulkner SH et al. Temperature (Austin). 2017. PubMed 28944271 · DOI · Free full text
- Who
- Lean (BMI 23.5) and overweight (BMI 29.2) men
- What
- 60 min hot-water immersion vs 60 min moderate cycling
- Protocol
- 104 (water) °F · 60 min · single session/wk
- Measured
- eHSP70, IL-6, energy expenditure, post-meal and 24-h glucose
- Result
- Energy expenditure +61.0 kcal/h (79%) during immersion; peak post-meal glucose 6.3 vs 6.8 mmol/L (113 vs 122 mg/dL) after immersion vs exercise (p<0.05); no difference in 24-h glucose AUC.
- Limitations
- Acute; small; lean and overweight men combined; no untreated control.
Hydrotherapy for Overweight and Obesity: A Systematic Review of Anthropometric and Lipid Outcomes.
B M et al. Cureus. 2026. PubMed 42781584 · DOI · Free full text
- Who
- 10 intervention studies in people with overweight or obesity
- What
- Hydrotherapy and water-based interventions, including sauna, steam bath and immersion (passive) and aquatic exercise (active)
- Measured
- Anthropometric and lipid outcomes
- Result
- Active aquatic exercise showed the most consistent improvements; passive hydrothermal interventions showed variable anthropometric and lipid findings; certainty of evidence low to low-to-moderate.
- Limitations
- Few passive-heat studies; heterogeneous; inconsistent adverse-event reporting.
Influences of Aerobic Exercise Training and Half Bath on Blood Component, Cardiorespiratory Function, and Vascular Compliance of Middle-aged Obese Men
Kim SS et al. Journal of Digital Convergence. 2012. Not in PubMed: sourceKorean publication; title and summary translated by SaunaLMN. Original title: 유산소성운동과 반신욕처치가 비만 중년남성의 혈액성분, 호흡순환기능 및 혈관탄성에 미치는 영향
- Who
- Middle-aged men with obesity (Korea)
- What
- Half-body bath for 12 weeks (n=10) vs aerobic exercise (n=10) vs no-treatment control (n=10); bath temperature and schedule not given in the abstract
- Protocol
- 12 wk
- Measured
- Blood lipids, maximal oxygen uptake, maximal heart rate and ventilation, vascular compliance
- Result
- The half-bath group differed significantly from controls in triglyceride, LDL-C and HDL-C and had better vascular compliance in arms and legs, but did not differ from controls in maximal oxygen uptake, maximal heart rate or maximal ventilation; aerobic exercise improved all blood components and cardiorespiratory measures more.
- Limitations
- 10 per group; allocation method not stated; weight change and bath protocol not reported in the abstract; article in Korean.
Protocols used in the studies
The RCT used hot bathing at a public bath facility twice weekly for 3 months (temperature not stated in abstract). Repeated hot-water immersion used 102 F (39 C) water for 1 h, 10 sessions over 2 weeks. Dry sauna studies used 194-196 F (90-91 C), either 15 min twice daily for 4 days or four 10-min sessions in one visit. Acute crossover studies used 30-60 min of hot-water immersion at 104 F (40 C) compared with cycling. A Korean controlled trial used half-body bathing for 12 weeks (temperature and frequency not given in the abstract).
What is still unknown
Whether repeated sauna or hot-water immersion over months changes weight, fat mass, blood pressure or glycemic markers in randomized controlled trials; whether heat adds anything to diet and exercise; tolerability in severe obesity and in people unable to exercise.
Safety
Cautions for sauna in this condition
- Body mass lost during sauna is mainly sweat: 0.65 kg after four 10-min sessions (PMID 30800676) and about 3% of body mass after 2 h (PMID 9383124); fluid replacement is needed and weight change after a session is not fat loss.
- Heart rate and blood pressure responses during repeated sauna sessions were larger in men with more body fat and larger body size (PMID 30800676).
- Hot-water immersion raised heart rate by about 33 bpm and lowered post-session blood pressure (PMID 42762318); orthostatic precautions apply with antihypertensives. No adverse events were reported in an 8-session dry-sauna study (PMID 32434303).
- See the sauna general safety entry for cardiovascular contraindications.
For clinicians
Suggested rationale
Passive heat alone has not produced weight loss in overweight or obesity (Sakurai 2013 RCT; Choi 2020); small studies show modest reductions in fasting glucose and insulin after 2 weeks of hot-water immersion (Hoekstra 2018) and acute blood pressure and vascular responses. Evidence supports at most an adjunctive role alongside diet and exercise, not a weight-loss treatment.
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