Exercise is an important part of any weight management paradigm. Aerobic exercise should be prescribed for every person attempting to lose weight and a resistance training program used to support metabolism. Weight loss via dietary restriction alone negatively impacts metabolism. Hypometabolism increases with caloric deficient diets beyond what would be expected from the loss of fat free mass (FFM). This state of hypometabolism causes energy conservation which makes dietary restriction less efficient over time. In a calorie reduced diet, when an individual reaches about 10% weight loss, total energy expenditure (TEE) decreases beyond what could be expected due to deceases in FFM. This reflects the body becoming increasingly energy conserving which slows weight loss or leads to the plateau phenomena.
Individuals with morbid obesity are less likely to well-tolerate weight bearing activities. Given this, for morbidly obese individuals, the most prudent strategy for weight loss is to combine moderate caloric restriction with appropriate increases in non-exercise physical activity, leisure-time physical activity and prescribed aerobic and resistance exercise. In regards to prescribed exercise, experts recommend a gradual progression accumulating 30 to 60 minutes of exercise on most days to a total 150 to 300 minutes per week in order to lose and maintain weight loss. The independent influence of resistance training and weight loss is not clear.
Resistance training may provide the following benefits for the person in a weight loss attempt:
1. It may maintain or increase muscle mass
2. It may increase resting metabolic rate (RMR)
3. It may increase fat oxidation post exercise
4. It may support aerobic training
5. It may improve leptin resistance
6. Improves muscular strength
7. Reducing in health risk
Muscle mass and RMR
Muscle is metabolically active tissue. In other words, it uses lots of energy. As muscle mass decreases so does metabolic rate. If weight training stimulus is enough, muscle hypertrophy can occur. Increases in muscle fiber size have been demonstrated with resistance training. This increase in muscle has been associated with increases in resting metabolic rate.
Resistance training may improve body composition by increasing fat oxidation. It has been demonstrated that a resistance training program with sufficient stimulus may decrease visceral obesity.
Supports aerobic exercise
During concurrent training (endurance & resistance training), resistance training has been shown to improve aerobic capacity. Additionally, circuit type resistance training programs can expend up to 9 kcal/min and improve aerobic capacity independent of endurance training, albeit less.
The neurohormone leptin is involved with signaling the brain regarding energy states in the body. It has been identified that some people with obesity have high leptin levels but their brains are not receiving the messages that they have enough energy. This state has been termed “leptin resistance”. It has been demonstrated that resistance training, aerobic, and combined training have improved leptin resistance.
Individuals who have higher levels of muscular strength generally weigh less then their weaker counter parts. This makes sense since muscular fitness is correlated with spontaneous physical activity. Additionally, persons with superior strength most likely have a greater muscle mass then those who are obese.
Reduction in health risk
Resistance training has been associated with lower rates of cardiovascular disease, improved blood lipid profiles, improved glycemic control, lower risk for musculoskeletal injury, and improved body image and mental health.
When thinking of weight control and exercise we tend to view it in the light of energy expenditure. However, one can see that as overweight and obesity are complicated issues, resistance training can influence more than simply how many calories are burned. If we were to reduce exercises impact to only calories burned we would be doing this important intervention a disservice.
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