We all want a quick fix. Our busy lives don’t allow us the time for being patient anymore, do they? We can get away with quick fixes in lots of things but for others, such as weight loss, it just doesn’t cut it. When we want to drop weight the quickest, we imply that we don’t care what weight we lose. The quickest way to lose weight is therefore a reduction in both available types of body mass: muscle and fat. However, we quickly have a problem. Loosing fat is great but if the available muscle is reduced, resting metabolic rate (RMR) is reduced proportionally (Speakman & Selman, 2003) which hinders continued fat loss and reduces the chances of keeping the weight off in the long term.
Here’s why. Net caloric intake at the 24 hour mark is the most important factor for weight loss. This is the amount of calories expended per day subtracted from the amount of calories consumed per day, and we want a negative number to lose weight. In terms of amount of calories burnt each day, resting metabolic rate (RMR) is very important. RMR is the amount of energy your ACTIVE cell mass expends to survive at rest, and is the dominant component for daily expenditure (accounts for around 60 -70% of the total calories that you burn every day) (Stiegler & Cunliffe, 2006). Simply put, it is how many calories you would expend if you simply lay down and did nothing for 24 hours.
By very definition we know that RMR must be associated heavily with body mass or more specifically fat-free or lean (muscle) mass. This is because the more muscle mass (active cells) we have, the higher the RMR will be (it is important to note that changes in fat mass will alter RMR but not as significantly as muscle mass will)(Frey-Hewitt et al., 1990). A reduction in total body mass will resultantly reduce RMR. As we want to keep the amount of calories burnt per day high, a reduction in RMR is not optimal, but it is a bi-product of reducing your body weight (figure 1; (Stiegler & Cunliffe, 2006)). We can however have an influence over the magnitude of this RMR decrease, by focusing on reducing just fat and maintaining or increasing muscle as much as possible. This is done through two simultaneous methods, the first being optimal macronutrient (fat, carbohydrate and protein) amounts to create the energy deficit needed to loose fat. We’re talking about a reduction of your net caloric intake by 10-15% of your daily maintenance requirement to loose fat and spare muscle, but also ensuring correct macronutrient proportions to foster muscle growth/maintenance. The second method is to undergo aerobic exercise at an intensity that maximises rate of fat burnt. You can find out what this intensity is for you by performing a VO2 max, Lactate and Energy Usage analysis assessment with us (more info at http://www.peakcentrevancouver.ca/vo2-max-blood-lactate-and-energy-usage-analysis/.).
Maintaining RMR as much as possible during a period of weight loss is critical to long term success, as your body composition (how much fat and muscle you have) following weight loss will impact RMR once you return to a maintenance caloric intake. To illustrate this, if a person reduced their body mass by 10kg through a fat loss of 8kg and a muscle loss of 2kg, their RMR would not be heavily reduced. Conversely, if the same individual were to lose 10kg body mass but through a 5kg fat loss and 5kg muscle loss, their RMR will be reduced to a greater degree. Once the individual returns to a maintenance calorie diet post-weight loss, the first condition would lead to a greater chance of sustained weight loss, as total caloric expenditure per day is greater by default than condition two.
Here at Peak Centre Vancouver, we focus on losing weight the right way through a reduction in fat and a maintenance or increase in muscle mass. It may take a little longer but your long term success is key to us and by putting the science back in to weight loss, we can ensure you will find the service you’ve been looking for. To learn more about RMR and assessment, head over to our page at http://www.peakcentrevancouver.ca/resting-metabolic-rate-and-body-composition-assessments/ and check out our program ‘Mission Possible’ at http://www.peakcentrevancouver.ca/services/weight-loss/ where we combine the latest exercise science with informed calorie restrictions to create the most comprehensive program for you.
Frey-Hewitt, B., Vranizan, K. M., Dreon, D. M., & Wood, P. D. (1990). The effect of weight loss by dieting or exercise on resting metabolic rate in overweight men. International journal of obesity, 14(4), 327-334.
Speakman, J. R., & Selman, C. (2003). Physical activity and resting metabolic rate. Proceedings of the Nutrition Society, 62(03), 621-634.
Stiegler, P., & Cunliffe, A. (2006). The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss. Sports Medicine, 36(3), 239-262.