Metabolism (also known as metabolic rate) is the rate at which your body inherently burns calories to fuel vital functions like breathing, blood pressure regulation, heart function, and brain activity. These calories are obtained from three essential macronutrients (carbohydrates, fat, and protein) housed in the foods you eat. In and of itself, metabolism is one of the most important factors in weight loss, weight gain, and long-term weight management.
The average metabolic rate is known to be at or around 1,200-1,500 calories per day for an adult woman and 1,500-1,800 calories per day for an adult man. This is the minimum amount of daily calories that’s generally recommended for sustaining vital bodily functions.
However, metabolism varies widely from person to person, as it’s influenced by a number of factors ranging from gender and age to physical characteristics (height and weight) and physical activity habits. For instance, taller people tend to have higher metabolic rates than short people while individuals who are overweight generally have higher metabolic rates than those who are not since more calories are needed to sustain a heavier body.
Lean muscle mass is also very closely linked to metabolism. The more muscle you have, the higher your metabolic rate tends to be at rest and during any types of physical activity. This is one of the reasons why women typically have lower metabolic rates than men and, therefore, naturally burn fewer calories for any given activity.
You can easily estimate your metabolic rate and daily calorie needs using an online calculator.
I like SELF Nutrition Data’s BMI & Calorie Calculator, as it factors in a wide range of physical activity levels to provide a more accurate estimate of daily calorie needs. Simply plug in specific information about your age, gender, physical characteristics, and lifestyle habits and you’ll get a good indicator of your maximum daily calorie allowance. This can essentially serve as your baseline for determining the minimum amount of calories you take in day-to-day (or week-by-week).
For instance, the estimated allowance for an inactive (sedentary) 30-year old woman standing 5 feet 6 inches tall and weighing 175 pounds is at or around 2,140 calories per day. This is the maximum amount of daily calories she can take in for weight maintenance. Now, the maximum allowance for a woman of the same age and stature, who regularly engages in vigorous exercises (running and weight lifting) could easily be in excess of 3,000 calories per day due to her extremely active lifestyle.
Needless to say, your daily calorie needs will also depend on your specific goals (weight maintenance, weight loss or weight gain).
In order to lose weight, you must continuously create deficits in the average number of calories you consume and the amount you burn. If you’re one with the ever so unique goal of gaining weight, you’ll have to create calorie surpluses by generally taking in more calories than you burn. For long-term weight maintenance, you must balance the number of calories you consume with the amount you burn, indefinitely.
So, the first woman in the example above would have to consistently eat less than 2,140 calorie per day to lose weight, more than that amount to gain it, and exactly that amount to maintain it.
A pound of fat houses an average of 3,500 calories. Therefore, if you create a 3,500-calorie deficit over a given period of time by eating less (dieting) and/or burning more (exercising) you’ll eventually lose a pound of fat. So, to lose 1-2 pounds in a week, you would reduce your daily food intake by 250-500 calories and then make an effort to burn an additional 250-500 with exercise and/or other forms of physical activity.
On the flip side, if you eat more calories than you burn and accumulate 3,500 calories over a given period of time, a surplus will occur resulting in a net weight gain of one pound. To gain 1-2 pounds in a week, you would take in an extra 500-1,000 calories per day (if you regularly exercise, you’d probably have to take in even more than that).
And, of course, when the amount of calories you consume is equal to the amount you expend, no weight gain or weight loss will occur (weight maintenance).
I should also mention that there are some other factors that can influence your body weight. These include the macronutrient composition of the foods you eat (low-carb, high-fat and/or high-protein), your stress levels, and whether or not you have a pre-exisiting chronic disease.
However, the premise behind metabolism and daily calorie needs remains the same.
Although some of this information might seem a bit complex, it’s really important for you to understand the basic concepts I’ve highlighted here. Whether you’re limiting your food intake, eliminating carbohydrates or even counting points, ALL popular dieting plans factor in your metabolic rate in order to manipulate your daily calorie needs in a way that leads to your losing weight, gaining it or maintaining it.
My goal here is to keep you better informed about the tools and tricks of the trade so that you feel more empowered to take control of your diet, your weight, and, ultimately, your health.