Does Weight Loss Always Improve Body Composition or Health?
Weight loss always seems to be at the top of the list of desired accomplishments for people at the beginning of a new year. There are many methods, or combinations of methods, that can be employed to lose weight - but not all will produce equal aesthetic and health-related benefits. Applying dietary modifications in conjunction with a combined resistance training and aerobic exercise program has been shown to be the best overall method for losing weight in a healthy manner. It is well documented that maintaining a negative caloric balance while ensuring the maintenance of lean mass is the optimal way to lose weight. Interestingly, the anaerobic component of exercise is the key to success as excess aerobic training causes a reduction in lean mass particularly when combined with caloric restriction.
A phenomenon that has received recent attention known as normal weight obesity is prevalent in people that unknowingly make poor choices when trying to meet their weight management goals. Normal weight obesity refers to the condition of having a significant level of body fat but presenting with what appears to be a “normal” or healthy weight. The problem with this combination of attributes is that the person has the similar levels of disease risk and may experience the metabolic or hormonal disturbances seen in a person who is visibly obese. Although these people do not look unhealthy externally, normal weight obesity has an increased risk of heart disease, diabetes, high cholesterol and dyslipidemia compared to an individual of identical weight whom is considered non-obese. Additionally, because the use of yo-yo diets with significant caloric restriction they also present with lower metabolisms than same weight individuals that are not obese. This clearly shows that body composition (the ratio of fat mass to fat free mass), not just body weight, is an essential component for attaining an optimal level of health and protection from disease.
Two common yet inappropriate methods people employ to lose weight quickly is starvation and/or an exercise program that emphasizes solely cardiovascular training.
Granted, for some individuals an aerobic-based training program may be an optimal starting point due the need to lose excessive weight for disease management or a specific pathology; but for most healthy adults - focusing on cardiovascular training alone will not elicit optimal results. Likewise there is a significant difference between 20 minutes of walking compared to 45 minutes of running. The main issue is that while cardiovascular training does expend the most calories per unit of time based on intensity; by itself it does not allow for optimal maintenance of lean mass. If an individual goes to the gym and only uses an elliptical machine or other cardiovascular modality without ever engaging in any resistance training, weight loss will be associated with both lipid and protein catabolism. The actual response is dependent on nutritional variables and the total volume of training, but it is well documented that body fat percentage is maintained to a greater extent with this behavior. The exerciser may be becoming thinner but with a decrease in both fat and lean mass.
High-volume cardiovascular training is prone to initiating metabolism of muscle tissue to synthesize necessary carbohydrates for energy – especially if calories are restricted during the training period. Therefore, it is crucial to incorporate some form of resistance training for the maintenance of lean mass due to the beneficial muscle and hormonal adaptations produced. To state it simply, complementary resistance and aerobic training can allow for significant weight loss while maintaining lean mass when proper nutrition is employed. Carbohydrate intake should reflect the given intensity and volume of training, and a slightly elevated intake of lean protein may be warranted.
Starvation and very low calorie diets will invariably deplete all carbohydrate storage forms including liver and intramuscular glycogen and blood glucose. When blood glucose is sustained at low levels for a given period of time the internal protein-sparing mechanism is lost and the body will spare remaining carbohydrate stores by breaking down and using structural proteins. This reaction is run by neurochemical and hormonal controls that cannot be modified. The stolen proteins are metabolized in the liver to produce new glucose via gluconeogenesis, which in turn raises serum glucose levels back to normal. Essentially, starvation can induce weight loss, but a great proportion of it will most likely be lean mass due to internal responses to low carbohydrates – another avenue for becoming “skinny-fat”.
Many individuals use the scale to determine their health status. As addressed previously, total body weight is not the primary determinant of associated risk of disease or health attainment. Body composition should be focused upon as elevated body fat with any morphologic dimensions will produce negative hormonal, metabolic, and cardiovascular effects. Interestingly, simply adding muscle produces a positive physiological response and consequent reduction in body fat percentage. Unfortunately, a recent study showed that around 20-30% of individuals who are considered of normal weight based on their BMI actually present with normal weight obesity when measured for body fatness. Personal trainers need to educate clients on the truths behind proper weight loss as it seems that the negative repercussions of being “skinny-fat” is not commonly understood in the standard weight-loss enthusiast.
