A recent Brazilian study published in PLOS One demonstrated how diet can impact the benefits of resistance training exercise.
Exercise and diet have been shown to be effective markers of overall health. Many studies have demonstrated the ability of exercise to prevent and treat a number of diseases. Specifically, diet and physical activity can act as predictors of obesity and metabolic health factors including insulin sensitivity and profile of blood lipids (such as cholesterol and triglycerides).
Both aerobic exercise and resistance training are beneficial for maintaining health. Though aerobic training has been more closely associated with weight loss, resistance training has been shown to help lower fat content in the body and build muscle mass. This change in fat and muscle composition can help lower the risk of disease.
Diet and the benefits of physical exercise are strongly connected
The benefits of physical exercise are strongly related to diet. This association has led to trends around specific exercise-diet regimens to manage body weight. For instance, low-carbohydrate, high-fat diets (LCD) are being used to promote rapid weight loss. These diets are commonly used in combination with resistance-training exercise. Some studies have shown that LCD can cause people to regain weight and fat deposits over long periods and that they might also affect factors of metabolic health such as insulin and glucose levels.
However, few studies have investigated the health effects of resistance training when used with LCD in the long term. In a recent Brazilian study published in PLOS One, researchers examined how resistance training in combination with long-term LCD impacted body weight, fat deposition, and metabolic health in rats.
In the study, researchers fed rats either a standard diet or an LCD for 21 weeks. The rats on the standard diet received 9% of calories from fat, 76% from carbohydrate, and 15% from protein. Those on the LCD had a diet of 59% fat, 31% carbohydrate, and 10% protein. After 10 weeks on either diet, the rats were further subdivided into sedentary and resistance-trained groups.
Sedentary rats were kept in their cages for the duration of the experiment without any type of exercise. Resistance-trained rates performed an 11-week exercise program that involved climbing vertical ladders with progressively heavier weights. Researchers monitored body weight, food intake, and other health indicators over the study period.
Effects of a low-carb diet on the benefits of resistance training
The results showed that resistance training lowered body weight and liver fat in both standard diet and LCD rats. In addition, resistance-trained rats on a standard diet had decreased abdominal fat deposits, lower LDL cholesterol levels, and improved muscle mass compared to sedentary rats. However, trained rats fed with LCD did not show a decrease in fat mass or improvements in muscle mass relative to their sedentary counterparts. Those fed with LCD also became more insulin resistant, meaning that they were less able to lower blood glucose levels. Lower rates of glucose uptake in LCD fed rats were partly caused by the decrease in muscle mass, which has a role in helping insulin remove glucose from the blood. These complications increase the risk of obesity and of developing type 2 diabetes.
More studies needed with human participants
Although long-term LCD had positive effects on body weight, the authors concluded that LCD prevented the ability of resistance training exercise to lower body fat, improve muscle composition, and regulate blood glucose levels. As a result, they suggest that resistance training in combination with long-term LCD may be harmful to human health. Future clinical studies on humans and on insulin resistance in specific body tissues will help confirm these results.
Written by Braydon Black, BSc
Reference: Stotzer US, Pisani GFD, Canevazzi GHR, Shiguemoto GE, Duarte ACGO, Perez SEA, et al. Benefits of resistance training on body composition and glucose clearance are inhibited by long-term low carbohydrate diet in rats. PLoS One [Internet]. 2018 Dec [cited 2018 Dec 29];13(12):e0207951. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207951 doi: https://doi.org/10.1371/journal.pone.0207951