How can metabolism be measured

CPT Weight Loss exercise science. As a certified personal trainer , this is a topic you may get asked about from time to time. This is an outcome of enhanced caloric expenditure, increased lean body mass, greater fat utilization and overall weight loss.

Scientific references to metabolism refer to the bodily processes needed to maintain life. But for most of us, it refers to total daily energy expenditure and how it influences our energy in versus energy out equation. Can we calculate our RMR? Can we influence it or is it predetermined? Resting metabolic rate is the total number of calories burned when your body is completely at rest.

RMR supports breathing, circulating blood, organ functions, and basic neurological functions. It is proportional to lean body mass and decreases approximately 0. Direct calorimetry measures the amount of heat produced by a subject enclosed within a small chamber to calculate energy expenditure. Indirect calorimetry measures oxygen utilization rates via gas analysis to calculate energy expenditure. Although direct and indirect calorimetry provide accurate estimates of RMR , these techniques are expensive , time consuming and difficult to access.

As a result, more accessible and affordable techniques that estimate RMR have been developed over the past years. They measure this value with varying degrees of accuracy. Perhaps the most common methods utilized today are mathematical formulas. You can access these with calorie calculators on the Internet, an app or through wearable devices. At first, this error appears small i.

Furthermore, these formulas also imply that all individuals of the same gender, age, height and weight have the same RMR, a fact that is certainly not accurate. Your lean body mass will significantly influence RMR and should always be considered. Although the Katch-McArdle and Cunningham formulas are derived from lean body mass rather than total body weight, they rely upon an accurate measurement on lean body mass.

Although newer equations continue to emerge e. Genetics and epigenetics can also play a significant role.

Over different genes have been identified by scientists that are related to obesity. The results of each test are analyzed using specific formulas that contrast oxygen inhalation and carbon dioxide exhalation. This allows your healthcare provider or trainer to estimate the number of calories you burn while at rest and during exercise. If you have lactate threshold testing done, your blood will be drawn at varying intervals during ever-increasing levels of aerobic activity, either on a treadmill or a bike.

Based on this information, you may decide to alter your physical activity or eating habits, so that you burn more or less calories daily. Metabolic testing can be valuable, but the results should only be looked at as part of an overall fitness or wellness program. Keep in mind that your test results provide a snapshot of your metabolism and fitness level on the day you were tested.

If your activity level changes, or your physical fitness improves or declines, your metabolic rate, and numbers, will change. Remember, the changes you experience will occur over time. You will likely not see any dramatic changes day to day. Luckily, metabolic rate can be sped up or slowed down safely by altering your lifestyle habits. There are several metabolic body types that are inherited. Your metabolic type may affect, to some degree, how easy it is for you to lose or gain weight.

Metabolic type is not, however, the only factor that determines physical appearance or weight. In fact, many people are a combination of several metabolic body types. In general, the three types are:. Scientific evidence about the best diets for metabolic body types is lacking, and not definitive. Anecdotally, it seems that endomorphs may experience insulin sensitivity more than the other groups.

Eating a diet low in carbohydrates, especially simple carbohydrates , may help. You can learn more about the endomorph diet here. Direct calorimetry requires the precise measure of heat output using a large, expensive and technically complex whole body calorimeter. Indirect calorimetry determines metabolic rate from the oxygen consumption of an individual.

Oxygen consumption measurements are typically done with a medical device called a metabolic cart. Measuring oxygen consumption, rather than using population-based predictive equations, allows health and fitness professionals to make the most accurate decisions for their clients. With a simple breath test of 10 minutes or less, an individual can now have their unique metabolism measured, for determination of a personalized calorie budget.

RMR is influenced by a number of factors, such as: body mass, body composition the amount of fat and muscle , age, gender and hormones. Muscle burns more calories than fat; a person with a higher percentage of muscle will have a higher RMR. At the same weight, similar height, and same age, these women have very different RMR values due to differences in body composition. Men normally have a higher metabolism than women, partly because they tend to have a higher percentage of muscle compared to women.

Certain hormones can also increase or decrease metabolism. The difference is more likely due to the way your rate was tested. Many gyms use a handheld device that measures the ratio of oxygen to carbon dioxide in your exhalations.

This reveals how efficiently you use oxygen, which in turn provides a window into your resting metabolic rate—how many calories you need just to maintain your body's functions.

The number can be valuable because resting metabolism accounts for about 70 percent of a person's calorie burn. Assuming you don't take in more calories than your body requires, exercise and activity use up another 15 to 20 percent of calories, and the rest help fuel digestion.

Unfortunately, any number of factors can skew the results.