Exercise is an effective method for weight management, disease prevention, and maintenance of several physiological parameters including the improvement of insulin resistance and obesity-induced risk factors in normal ‘healthy’ and obese individuals.
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What is weight training?
Regular physical activity can be defined as the movement of the body produced by the contraction of skeletal muscle that increases energy expenditure.
Weight training is a form of resistance exercise that refers to any form of exercise where the participant lifts or pulls against resistance. This form of training includes weight lifting and is performed to improve muscular strength, size, or endurance.
Several meta-analyses have shown a significant effect of both endurance and strength training on anthropometric (related to measurements and proportions) and cardiometabolic parameters. These include evidence to support the role of strength training in the alteration of body weight, body mass index (BMI), waist circumference, fat mass (FM), improved lipid profile, decreased glucose, insulin levels, and blood pressure (BP).
Effect of strength training on glucose and insulin homeostasis
Physical activity has been shown to improve glucose on insulin tolerance due to increased uptake of glucose by muscle mass. Moreover, components of glucose metabolism such as the density of insulin protein receptors, and key enzymes involved in the metabolism of glucose or adjusted positively.
Although strength training alone is known to exert positive effects on insulin metabolism, a study has reported that combined training, comprised of endurance training and resistance (weight) training, results in greater improvement in insulin sensitivity, b-cell function, and glucose effectiveness relative to endurance or strength training alone. Quantitatively, a 52% improvement in insulin sensitivity was observed by this combined training, which was retained over two weeks after the last training session.
Weight training and cardiovascular disease
Multiple studies have found an inverse relationship between strength training and heart disease. A study published in 2017 in Medicine and Science in Sports and Exercise (MSSE) found that among 35,000 women, those who performed resistance reduced their risk of developing Type 2 diabetes by 30% relative to those who did not.
Meanwhile, women who engaged in any amount form of resistance training reduced their risk of cardiovascular disease by 17%. A similar 2019 study also published in MSSE Demonstrated that weight training was associated with a decrease in cardiovascular disease, including attack, stroke, and increased longevity. In this study, approximately 13,000 people performing resistance training for less than an hour per week were found to decrease their risk of cardiovascular disease and all-cause mortality by 40-70%.
Moreover, a study published in JAMA Cardiology concluded that strength training in sedentary adults with obesity experienced a decrease in pericardial adipose tissue (a form of tissue deposit's surrounding the heart; and the form correlated with heart disease and stroke) by 32%. This only occurred in the group that performed strength exercises, not the group that performed aerobic exercises. However, both groups experienced a decrease in epicardial adipose tissue, the other form of fat deposit surrounding the heart.
The effect of weight training on cancer
Cancer is the leading cause of morbidity and more mortality across the world accounting for approximately 14 million new cases and 9.6 million cancer-related deaths worldwide. Data from the Health Survey for England which queried 80,000 adults over the age of 30 demonstrated that adhering to resistance exercise training at least two times per week was associated with a decreased risk of cancer mortality of 34%.
This effect was not seen in adults who adhered to aerobic training. Moreover, cancer survivors who regularly engaged in resistance training (at least once a week) showed a 33% reduction in all-cause mortality. Although studies are observationally, and causation cannot be determined, they support the notion that the performance of resistance exercise training can reduce cancer risk and cancer recurrence.
Resistance exercise training by way of weight training has also been shown to alleviate side effects associated with cancer treatment. Most common therapeutic approaches to therapy include radiation, chemotherapy, and androgen therapy for prostate cancer.
These increase the loss of skeletal muscle mass, with a subsequent decline in the strength of patients. In addition, these changes also have negative outcomes for clinical endpoints including cancer mortality, disease progression, and complications as a result of therapy ie dose-limiting toxicity.
Resistance exercise training that engages the whole body can preserve muscle mass in patients with prostate cancer who are undergoing androgen deprivation therapy all radiation therapy according to a study published in 2010.
Moreover, data from in a supervised trial of aerobic versus resistance training (START) has demonstrated that whole body, progressive resistance training (three sets at 60-70% of one-repetition maximum) improved strength, fatigue, lean body mass, and the rate of chemotherapy completion in breast cancer survivors that were undergoing adjuvant treatment.
There was no difference in those who engaged in aerobic training or usual care. These findings have been corroborated in a recent meta-analysis of 11 randomized control trials in which 1167 participants receiving treatment for a range of cancers demonstrated improvements in lean body mass, strength, and whole-body fat mass when regularly performing resistance training.
Regular physical activity in the form of resistance/weight-based training can prevent or reduce the risk of many age-related diseases. There is some understanding of the molecular bases that underpin the health benefits of exercise and demonstrate that weight training is a potent countermeasure against declines in mobility, metabolism, physiology, and mortality.
References:
- Christensen RH, Wedell-Neergaard A, Lehrskov LL, et al. (2019) Effect of Aerobic and Resistance Exercise on Cardiac Adipose Tissues: Secondary Analyses From a Randomized Clinical Trial. JAMA Cardiol. doi:10.1001/jamacardio.2019.2074.
- Liu Y, Lee DC, Li Y, Zhu W, et al. (2019) Associations of Resistance Exercise with Cardiovascular Disease Morbidity and Mortality. Med Sci Sports Exerc. doi:10.1249/MSS.0000000000001822.
- Shiroma EJ, Cook NR, Manson JE, et al. (2017) Strength Training and the Risk of Type 2 Diabetes and Cardiovascular Disease. Med Sci Sports Exerc. doi:10.1249/MSS.0000000000001063.
- Kirwan JP, Sacks J, Nieuwoudt S. (2017) The essential role of exercise in the management of type 2 diabetes. Cleve Clin J Med. doi:10.3949/ccjm.84.s1.03.
- Stamatakis E, Lee LM. Bennie J, et al. (2018). Does strength-promoting exercise confer unique health benefits? A pooled analysis of data on 11 population cohorts with all-cause, cancer, and cardiovascular mortality endpoints. Am J Epidemiol. doi:10.1093/aje/kwx345.
- Cormie P, Zopf EM, Zhang X, et al. (2017) The Impact of Exercise on Cancer Mortality, Recurrence, and Treatment-Related Adverse Effects. Epidemiol Rev. doi:10.1093/epirev/mxx007.
- Ruiz JR, Sui X, Lobelo F, et al. (2009) Muscular strength and adiposity as predictors of adulthood cancer mortality in men. Cancer Epidemiol Biomarkers Prev. doi:10.1158/1055-9965.
- Galvão DA, Taaffe DR, Spry N, et al. (2010) Combined resistance and aerobic exercise program reverses muscle loss in men undergoing androgen suppression therapy for prostate cancer without bone metastases: a randomized controlled trial. J Clin Oncol. doi:10.1200/JCO.2009.23.2488.
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