By Registered Dietitian, Jeannie Versagli
Ever wonder why some individuals can eat anything without gaining a pound, while others seem to only have to look at food to gain weight? Individuals metabolize foods differently; muscle mass, age, and physical activity are just some of the reasons for these differences. Metabolism is the process by which our bodies convert the food we eat into the energy needed for survival and function.
Each one of us has a rate at which we burn calories at rest, known as our Resting Metabolic Rate (RMR). A person’s RMR will vary depending on genetic predisposition, body size, gender, and age. Surprisingly, we burn approximately 60-75% of the energy used each day for our RMR. This is the energy our bodies burn to maintain themselves at rest. Functions of our bodies at rest include our heart beating, breathing, digestion, and sleeping, to name a few. Every bit of physical activity that we perform throughout the day requires additional calories other than those needed for RMR.
Activity affects how many calories you will burn; for example, jobs involving gardening, walking, and lifting require more energy than individuals with sedentary jobs, like sitting at a desk all day. Since studies have shown that standing burns more calories than sitting, there has been an uptick in the purchase and use of standing desks in an attempt to increase energy expenditures throughout the work day. At the end of the day, the goal here is to meet the necessary energy requirements to fulfill our RMR needs along with the additional calories to perform activities of daily living, all while maintaining a healthy weight. There are many factors affecting our RMR, some of which we have control over and others, not. Let’s explore these factors influencing our RMR.
The natural process of aging causes muscle to turn into body fat. Because our RMR slows down with age, it is critical that we understand the aging process and our individual metabolism. Fat cells do not require as many calories to function compared to muscle; as we age, therefore, less calories are needed to maintain RMR. We can combat the negative outcome of aging by increasing physical activity and maintaining proper nutrition.
Exercise increases your body’s need for calories. The intensity and length of exercise determines the fuel source utilized and the number of calories burned. The ideal scenario is for an individual to burn a combination of fats and carbohydrates for fuel, as this allows muscle mass not to be utilized as a fuel source.
Muscle vs. Fat Ratio
Men burn more calories in general because they have a higher lean-body-mass-to-fat ratio than women. The more muscle mass an individual maintains, the greater the demand for calories. Muscle requires constant fuel, where fat requires little fuel to sustain itself. Eating the appropriate amount of macro nutrients (carbohydrates, proteins and fat) combined with exercise can influence the rate at which your metabolism utilizes calories.
A hormonal imbalance can greatly affect the rate at which you burn calories. Your thyroid is responsible for regulating your metabolism. If you are struggling with unexplained weight gain or weight loss, see your physician. You may have hypo (low) or hyper (high) thyroidism.
One of the golden rules to set your metabolism for the day is to start out with breakfast. Consuming breakfast gets your metabolism going. Studies indicate that an individual can increase their metabolism by 10% for that day by including breakfast. When you don’t eat breakfast, you’re fasting for 15 to 20 hours, suggesting to the body that starvation is occurring thereby sending a signal to the body to slow down the rate at which it will burn calories.
Always stay hydrated! Dehydration can contribute to ineffective metabolism. Some studies suggest that your body temperate drops slightly when you are dehydrated, causing your body to store fat to maintain normal temperatures. Other studies have indicated that dehydration resembles fasting and therefore lowers your metabolism.
Fresh fruits, vegetables, and whole grain products take longer to digest. Incorporating these foods into your diet will aid in increasing your metabolic rate and provide you with nutrient-dense foods. Spicy foods, such as hot peppers, have been known to increase metabolism for 30 minutes or so after consumption.
The processes of digesting, absorbing, transporting, and storing of carbohydrates and protein requires energy. About 10% of the calories from these nutrients are used during the Thermogenesis process. If your diet if high in fat, you will be burning less calories.
Next time you find yourself wondering how others may be able to consume more calories than you, think about what are you doing to positively influence your metabolic rate. Are you physically active, maintaining a healthy weight, consuming adequate carbohydrates, proteins and fats, adequately hydrated, and eating breakfast? You can influence the rate at which you burn calories to some degree by being mindful of your daily physical activities, what time you begin your meals each day, what types of foods you consume, how many calories you consume, and how well you hydrate. Remember that age and gender continue to affect your RMR throughout your lifetime.
Jeannie Versagli holds a license in Nutrition for the state of Delaware and is a Registered Dietitian with the Academy of Nutrition and Dietetics, a national professional organization. Her career in the Nutrition and Culinary fields spans over 30 years. As a part of the HAC team, Jeannie oversees our nutrition programs and services, facilitates some of the services personally, and acts as a resource throughout the club.