Exercise as Medicine: What the Oncology Evidence Now Tells Us
- Jun 24
- 5 min read
For most of my career, the standard advice given to individuals with cancer was simple: rest, eat what you can, and focus on getting through treatment. It was well-intentioned. It was also incomplete.
The science has moved. We now have consensus-level evidence that structured exercise during active cancer treatment is not only safe for most adults but also meaningfully improves outcomes. The 2022 American Society of Clinical Oncology (ASCO) guideline on exercise, diet, and weight management during cancer treatment makes this explicit, summarizing dozens of randomized trials and systematic reviews showing improvements in fitness, fatigue, mood, and overall quality of life.
I recently sat down with Sami Mansfield, an amazing Cancer Exercise Specialist, founder of Cancer Wellness for Life, and a co-author of those ASCO guidelines, to explore what this evidence means in practice, especially for midlife adults, and women navigating natural or treatment-induced menopause. The full conversation is available on the Thrive on Plants podcast and YouTube.
Muscle as an Endocrine Organ: Why Exercise Changes the Biology
One of the most important reframes, both in this conversation and in the literature, is that skeletal muscle is not just “tissue that moves us.” It is a metabolically active endocrine organ.
When we exercise, especially with resistance training and higher-intensity intervals, contracting muscles release signaling proteins called myokines into the bloodstream. These include IL‑6, irisin, and other myokine-related factors. Research shows that myokines can dampen chronic inflammation, improve insulin sensitivity, and influence immune function in ways that are directly relevant to cancer biology. Physical inactivity, excess visceral fat, and pro-inflammatory cytokines such as TNF‑alpha help create a tumor-favoring environment; regular exercise is one of the few tools that directly changes that environment at the molecular level.
This is why “just move” is not soft advice. It is a biochemical intervention.
The Hidden Crisis: Sarcopenic Obesity
A second insight from our discussion is the growing recognition of sarcopenic obesity, a state where excess fat mass masks significant muscle loss.
In a 2025 study of women with non-metastatic breast cancer, Mialich and colleagues used CT-based skeletal muscle index and bioimpedance-derived Phase Angle, a marker of cellular integrity, to assess prognosis. Women with low muscle mass and lower Phase Angle had significantly worse survival, even when BMI looked “fine” or high. In other words, body weight alone failed to capture who was truly at risk.
For clinicians and health professionals, the implication is straightforward: BMI is not enough. We should be assessing muscle quantity and quality, Phase Angle where available, and visceral fat distribution, especially in midlife and older women.
Treatment-Induced Menopause: Different Biology, Different Prescriptions
We also spent time on treatment-induced menopause, a distinct clinical entity that is often lumped together with natural menopause in general wellness messaging.
Natural menopause unfolds over years. Treatment-induced menopause, triggered by chemotherapy, oophorectomy, or long-term endocrine therapy, is often abrupt. The sudden loss of estrogen accelerates muscle loss, worsens bone health, and shifts fat from peripheral to visceral depots. Many women experience faster weight gain, decreased strength, and higher cardiometabolic risk, even when their diet has not dramatically changed.
In this context, resistance training is not “just a lifestyle tip.” Mechanical loading directly stimulates muscle protein synthesis and related pathways independent of circulating estrogen. For women on aromatase inhibitors or tamoxifen, regular progressive strength training becomes one of the few reliable anabolic signals they still control.
Prevention Is Daily, Not Just Diagnostic
Perhaps the broadest reframe applies to everyone, regardless of cancer history. Screening tests, mammograms, colonoscopies and PSA tests are detection tools. Prevention is what happens in between those appointments.
The 2018 World Cancer Research Fund / American Institute for Cancer Research report estimates that roughly 30–50% of cancers could be prevented through modifiable lifestyle factors, including physical activity, body weight, diet, alcohol, and tobacco. Large cohort analyses and recent work with WCRF/AICR scoring systems consistently show lower cancer and all-cause mortality in people who adhere more closely to these recommendations.
Patterns that emerge as most protective include:
Regular physical activity, including both aerobic movement and strength training
Maintaining a healthy body weight and minimizing visceral adiposity
A whole-food, plant-predominant diet rich in vegetables, fruits, whole grains, beans, nuts, and seeds, with limited red and processed meat and ultra-processed foods
Minimizing alcohol and avoiding tobacco
These are not guarantees, but they are powerful risk modifiers.
From this evolving evidence base and our conversation, a few practical principles stand out:
Prescribe, don’t just suggest. Written, specific exercise referrals, ideally to professionals trained in cancer exercise, carry more weight than vague encouragement.
Make resistance training non-negotiable in menopause and endocrine therapy. Two to three sessions per week of progressive strength training help preserve lean mass, improve insulin sensitivity, and support functional independence in midlife women, especially those facing abrupt estrogen loss.
Aim for higher protein intakes in older, sarcopenic, or oncology patients. The 0.8 g/kg/day RDA is often inadequate in these populations. Emerging guidelines for older adults and sarcopenia support intakes of 1.0–1.2 g/kg/day, and 1.2 g/kg/day or more in frail or sarcopenic individuals, which are achievable with thoughtfully planned whole-food, plant-based diets.
Start where the patient is. For many people undergoing treatment, the barrier is behavioral and emotional, not physiological. Beginning with five minutes of daily movement and scaling up as capacity and confidence grow is often more effective than prescribing ideal, but unrealistic, programs.
Screen for body composition, not just weight. When feasible, incorporate measures of muscle and Phase Angle into assessment and pay attention to subtle functional declines, grip strength, gait speed, and difficulty with daily tasks, which may signal sarcopenia even in higher-BMI patients.
The question in oncology is no longer whether exercise and lifestyle matter. The question is whether we will restructure care so that movement, nutrition, and body composition sit alongside chemotherapy and targeted drugs as standard components of prevention, treatment, and survivorship.
That is the shift our patients, and their future healthspan, deserve.
Be well,
Daphne
#ExerciseOncology #CancerPrevention #LifestyleMedicine #WomensHealth #Longevity #PlantBased #MenopauseHealth #Sarcopenia #ThriveOnPlants #WingmanWellness
References
Campbell KL et al. Exercise, Diet, and Weight Management During Cancer Treatment: ASCO Guideline. Journal of Clinical Oncology. 2022. https://ascopubs.org/doi/10.1200/JCO.22.00687
Mialich MS et al. Skeletal muscle index and Phase Angle as predictors of mortality in nonmetastatic breast cancer. PubMed PMID: 40014176. 2025.
ASCO Annual Meeting 2025. Physical activity and recurrence in stage III colon cancer survivors (CALGB/SWOG 80702 cohort data).
American Institute for Cancer Research / World Cancer Research Fund. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective. 2018. https://www.wcrf.org/dietandcancer
Pedersen BK, Febbraio MA. Muscles, exercise and obesity: skeletal muscle as a secretory organ. Nature Reviews Endocrinology. 2012;8(8):457-465.
Thrive on Plants Podcast, Episode with Sami Mansfield. YouTube: https://youtu.be/TgejRseWGcE?si=ASnjMAtl8iI11mt_ | Apple Podcasts and Spotify: search Thrive on Plants.
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