Dr Mercola on Weight Training: A Reply to Mrs Vera West, By John Steel and Brian Simpson

While we agree with the main points that Mrs West makes drawing on Dr Mercola's piece on how weight training helps prevent dementia, we do not agree with his minimalist claims that training for over 120 minutes a week is worse than doing nothing at all. Here we set out the case against this.

The Real Research on Resistance Training and Longevity

While O'Keefe's research does discuss potential risks of excessive endurance exercise, the claims about resistance training being harmful after 2+ hours per week are not supported by the broader scientific literature. The largest and most comprehensive studies show a different picture entirely.

What the Meta-Analyses Actually Show

A 2022 systematic review and meta-analysis, the gold standard of scientific evidence, examined multiple studies involving hundreds of thousands of participants and found that resistance training is associated with reduced risk of all-cause, cardiovascular disease, and cancer-specific mortality, with any amount of resistance training reducing the risk of all-cause mortality by 15%.

The same analysis found that maximum risk reduction of 27% was observed at around 60 minutes per week of resistance training, with mortality risk reductions diminishing at higher volumes, but notably, the benefits diminish rather than reverse into harm as Mercola claims.

The J-Curve Misinterpretation

While some research does suggest a J-shaped curve for certain types of exercise, the interpretation matters greatly. Higher resistance exercise volumes were associated with diminishing benefits, reaching zero benefit at around 150 min per week, with weekly volumes above 150 min shown to increase mortality risk. However, this is 150 minutes (2.5 hours), not the 130-140 minutes Mercola claims, and the increase in risk brings people back to baseline, not worse than sedentary individuals.

Critical Problems with Mercola's Claims

1. Cherry-Picking and Misrepresentation

Mercola appears to be taking specific findings about endurance exercise and inappropriately applying them to resistance training. O'Keefe's research primarily focused on excessive endurance exercise (like ultra-marathons), not moderate resistance training.

2. Ignoring Dose-Response Evidence

Resistance training is associated with lower mortality and appears to have an additive effect when combined with aerobic exercise. The research consistently shows benefits that plateau at higher volumes, not a dramatic reversal into harm.

3. Contradicting Real-World Evidence

Mercola's claims fly in the face of:

Historical evidence: Manual labourers throughout history who performed hours of physically demanding work daily.

Contemporary populations: People in developing countries who engage in heavy physical labor and demonstrate good longevity.

Athletic populations: Studies of strength athletes don't show the dramatic mortality increases Mercola describes.

4. Ignoring Biological Plausibility

The mechanisms by which resistance training benefits health, improved muscle mass, bone density, metabolic health, insulin sensitivity, and cardiovascular function, don't suddenly reverse at arbitrary time thresholds.

What the Science Actually Recommends

The research suggests that for longevity:

Aim for two sessions/week of strength training for a cumulative time of about 40 to 60 mins/week, ideally not exceeding 150 mins/wk

Benefits plateau rather than reverse at higher volumes

Guideline-concordant strength training is significantly associated with decreased overall mortality

The Bottom Line

While there may be diminishing returns to very high volumes of resistance training, the idea that 2+ hours per week makes you worse off than being sedentary is not supported by the weight of scientific evidence. The largest, most comprehensive studies show consistent mortality benefits from resistance training, with optimal benefits around 60 minutes per week and diminishing (but not reversing) benefits at higher volumes.

Mercola's dramatic claims about resistance training being worse than sedentary behaviour at moderate volumes contradict:

Multiple large-scale meta-analyses

Decades of exercise physiology research

Real-world population health data

Basic biological understanding of how resistance training affects the body

The scientific consensus remains clear: regular resistance training, even at volumes exceeding Mercola's suggested limits, is beneficial for longevity and health outcomes. While there may be optimal dose ranges, the evidence does not support the claim that moderate resistance training volumes become harmful to longevity:

Momma, H., Kawakami, R., Honda, T., & Sawada, S. S. (2022). Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies. British Journal of Sports Medicine, 56, 755-763.