Myth 1, "lifting weights will make you bulky." The meta-analytic evidence supports the general direction of this correction while complicating the wording. Absolute increases in muscle size slightly favoured males compared to females (SMD = 0.19, 95% HDI: 0.11 to 0.28), however, relative increases in muscle size were similar between sexes, and outcomes were minimally influenced by the measure of muscle size and not influenced by resistance training experience of participants. Absolute hypertrophy of upper-body but not lower-body regions was favoured in males, and Type I muscle fibre hypertrophy slightly favoured males, while Type II muscle fibre hypertrophy was similar between sexes. A separate controlled trial found that in regard to relative changes, findings differ from absolute increases, where males often exceed females in absolute increase of muscle mass and strength given sex differences in baseline muscularity and force production. The commonly cited hormonal mechanism is that women naturally have significantly lower testosterone than men, typically five to ten times less, and this difference plays a major role in limiting the extent of muscle hypertrophy.

Important nuance: "relative gains are similar between sexes" is not the same as "women do not gain muscle." Women do build real muscle. The evidence supports that absolute muscle size gains are smaller, particularly in the upper body, not that hypertrophy does not occur.

Myth 2, "cardio is the best way to lose fat." This is where the post's framing runs into direct tension with the evidence. The 2025 meta-analysis concluded: while there are no differences in percent body fat loss between exercise modes, aerobic training and concurrent training are more effective than resistance training alone in reducing absolute fat mass; however, resistance training neither improved nor impeded fat mass loss when incorporated into concurrent training. The authors further noted that both aerobic training and concurrent training appear more favorable for fat mass loss compared to resistance training, and the absence of significant differences between aerobic and concurrent training suggests that combining aerobic and resistance exercise does not hinder the fat loss effect. A separate 2025 network meta-analysis found that under caloric restriction, aerobic exercise is more effective in reducing body fat than combined exercise or resistance training, aligning with trends observed under normal dietary conditions.

The counterweight that partly rescues the post's point: resistance training's distinct advantage is muscle preservation, not fat loss magnitude. Evidence indicates resistance exercise added to diet-induced weight loss had no effect on total weight loss (mean difference -0.32 kg, 95% CI -1.00 to 0.35, p=0.35) but did preserve fat free mass. A larger pooled analysis found that in 25 randomized controlled trials with 1,608 participants, adding resistance training to a calorie-restricted diet increased fat loss while preserving muscle mass. Additionally, resistance exercise is thought to increase basal metabolic rate by preserving lean body mass. Diet is also a major driver, with research suggesting that reducing calories ingested may be more important than increasing exercise for people looking to effectively manage weight.

Myth 3, "you need to work out every single day." This is the best-supported of the three corrections. WHO guidance states adults should do at least 150 to 300 minutes of moderate-intensity aerobic physical activity, or at least 75 to 150 minutes of vigorous-intensity activity, or an equivalent combination throughout the week, and should also do muscle-strengthening activities at moderate or greater intensity involving all major muscle groups on 2 or more days a week, a strong recommendation supported by moderate certainty evidence. On training frequency specifically, a review reported that ten studies using direct site-specific measures of hypertrophy generally reported that resistance training once per week elicits similar hypertrophy compared to training two or three times per week , though an earlier meta-analysis found a significant impact of training frequency on hypertrophy effect size (P = 0.002), with higher frequency associated with greater effect size (0.49 vs 0.30), indicating that frequencies of twice a week promote superior hypertrophic outcomes to once a week. Even the higher estimate is far below daily. On health outcomes, a pooled analysis found that between 30 and 60 minutes of muscle strengthening activity every week is linked to a 10 to 20% lower risk of death from all causes and from cardiovascular disease, diabetes and cancer, independent of aerobic exercise, with a J-shaped curve for most outcomes.