Low Calorie Diets, Fasting, and Longevity.

Does Building Muscle Shorten the Lifespan?

By: Lacey Dunn

Muscle needs fuel to grow and maintain. Building muscle generally requires a state of an energy surplus, while losing weight requires an energy deficit. Building muscle provides amazing benefits such as increasing your metabolic rate, decreasing your risk of osteoporosis, and reducing your risk for cardiovascular disease. Research shows that caloric restriction, fasting, and intermittent fasting are all 3 methods of dieting that could potentially lead to enhancing longevity and reducing the risk of age related chronic diseases. So are we shortening our lives by building muscle? How does fasting and caloric restriction come into play in the world of fitness? Diving into the research and these dietary methods gives us a glance of potential methods to prolonging our lives and how we can implement them safely while reaching our physique and fitness goals.

Caloric restriction is defined as energy restriction, calories significantly below the amount needed to maintain weight, without malnutrition. Studies show that caloric restriction may not only be a tool for weight loss, but may potentially provide a route for extending the life span and reducing chronic disease. An analysis of the literature on caloric restriction from Heilbronn and Ravussin showed several health benefits seen in animal models including normalizing blood glucose and leptin levels, stimulating growth hormone production, enhancing fat mobilization, lowering triglycerides, and reducing oxidative stress. These factors may contribute to reducing age related chronic diseases and enhancing longevity, but there is inconclusive evidence to its effects on humans and long term health.

The lack of human research on caloric restriction scatters conclusions to whether this method of dieting should be used and researchers suggest that this type of diet is probably not suitable for many individuals. Though there may be potential health benefits, caloric restriction poses many risks such as reducing metabolic rate, causing loss of lean muscle tissue, and potentially creating nutrient deficiencies, which could cause detrimental effects to. This makes caloric restriction an anti-aging method not suitable for anyone wanting to maintain or grow muscle and not the best method for any individual. A study done by Redman and Ravussin found that caloric restriction can cause the development of eating disorders, depressed mood, and create deficits in cognitive performance. Due to these negative effects, caloric restriction should be used solely as a tool for reducing weight that contributes to chronic diseases or poses a health threat and should not be done long term. Many of the health benefits associated with caloric restriction can be obtained by losing excess weight and living a physically active lifestyle which itself reduces your risk for metabolic disorders, diabetes, and cancer.

Unlike caloric restriction, fasting is another technique of dieting that shows promising results for reducing the risk of chronic disease, enhancing longevity, and creating positive results in body composition. There are many methods for fasting, such as timed feedings (intermittent fasting), alternative day fasting, and bi-weekly fasting. One of the most common methods involve time restrictive feeding, such implementing an 8 hour feeding window and a 16 hour fasting window within a 24 hour period. The most important factor in fasting is adherence and caution should be taken always when performing this type of diet. With fasting, the body has no direct fuel from food and it utilizes glycogen levels in the muscles and liver for energy. Once these stores have been depleted, the body turns to fat storage for energy and can turn to muscle protein as well if protein intake is insufficient. Many of the benefits seen from low calorie diets such as decreasing insulin sensitivity, increases fat mobilization, and decreasing blood lipid levels are seen with fasting methods. Research also shows that by implementing both a timed fasting method while resistance training, individuals may enhance changes in body composition. This result however is not conclusive throughout the literature.

In a study by Min Wei et al., a 5-day cycle of fasting showed a safe and effective way to reduce the markers of aging and age related disease such as blood pressure, fasting glucose, IGF-1, triglycerides, and C-reactive protein. If trying to maintain or build muscle, caution should be taken with any form of fasting to prevent muscle loss, however, studies show that when suffienient protein intake is present along with resistance training, loss of lean muscle tissue does not pose a problem. Tinsley et al. studied the concern of loss of lean mass due to fasting and examined the effects of fasting on body composition with resistance training. They found no difference in body composition changes or loss of lean muscle tissue in either group.

Although low caloric dieting, fasting, and intermittent fasting may show potential health benefits related to increasing the length of the lifespan and reducing chronic disease, the effects of aging and disease do not just come from the amount of calories consumed, but are determined by a variety of dietary, lifestyle, environmental, and genetic factors. Dietary interventions to achieve the “fountain of youth” still need more research and there is compelling evidence that maintaining a healthy body weight will contribute to a longer and healthier life. Individuals should focus on filling their bodies with nutritious, energy rich foods full of essential vitamins and minerals, while maintaining a healthy body weight if they are looking to extend their lifespan and feel their best. By getting in the gym and building muscle, rest assured that you are not shortening your life span, but providing your body with an activity that contributes to overall health, mood, and happiness.

References:
Heilbronn, K Leonie and Ravussin, Eric. Caloric restriction and aging: review of the literature and implications for studies in humans. Am J Clin Nurt 2003; 78:361-9.
Lee C, Longo V. Dietary restriction with and without caloric restriction for healthy aging. F1000Research. 2016;5:F1000 Faculty Rev-117. doi:10.12688/f1000research.7136.1.

Min Wei et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Science Translational Medicine. 15 Feb 2017. 9: 377.

Redman LM, Ravussin E. Caloric Restriction in Humans: Impact on Physiological, Psychological, and Behavioral Outcomes. Antioxidants & Redox Signaling. 2011;14(2):275-287.
Tinsley et al. Journal of the International Society of Sports Nutrition 2015, 12(Suppl 1):P38 http://www.jissn.com/content/12/S1/P38