Basal Metabolic Index. Basal Metabolic Rate. Weight loss. Body composition. Calorie deficit. The thermal effect of Food.
This terminology that gets bantered around that may or may not be well understood. This blog post attempts to explain and clarify the relationship between all of these factors and how best to increase your return on investment with regards the time you spend in the gym and in the kitchen, with the ultimate purpose to improve your health.
Understanding these concepts can empower you to make informed decisions about your fitness and nutrition strategies. Let’s delve into each term and uncover how they intertwine to impact your health journey.
Basal Metabolic Index (BMI)
BMI is a calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared. This index is widely used as a screening tool to categorise individuals into various weight categories such as underweight, normal weight, overweight, and obesity. While BMI can provide a quick snapshot of potential weight-related health issues, it does not differentiate between muscle and fat mass, nor does it account for the distribution of fat. Therefore, it should be considered alongside other measures like body composition and overall health indicators for a more comprehensive understanding of an individual’s health status.
Basal Metabolic Rate (BMR)
BMR refers to the number of calories your body needs to maintain basic physiological functions while at rest, such as breathing, circulation, and cell production. It accounts for the largest portion of your daily calorie expenditure. Factors like age, gender, genetics, and body composition influence your BMR. Knowing your BMR can help tailor your nutrition and exercise plans to meet your specific goals.
Weight Loss
Weight loss occurs when you burn more calories than you consume, creating a calorie deficit. It's a straightforward concept, but the execution requires careful planning and consistency. Understanding the balance between calorie intake and expenditure is crucial for sustainable weight loss. Applying both diet and physical activity to create this deficit ensures that the weight you lose is predominantly fat, rather than muscle or water.
Body Composition
Body composition refers to the ratio of fat mass to lean mass in your body. It's possible to improve your body composition by reducing body fat and increasing muscle mass. This is where strength training and protein-rich diets play vital roles. Focusing on body composition, rather than just scale weight, provides a more accurate picture of your health and fitness progress and is fundamental in achieving long-term sustainable health outcomes.
An improved body composition, i.e. an increase in muscle mass and a decrease in fat mass, will ensure your BMR increases. This in turn means that you will burn more calories at rest, and will ultimately lead to a reduction in body fat, or a reduction in body fat AND an increase in lean muscle mass.
Calorie Deficit
A calorie deficit is achieved when you consume fewer calories than your body needs to maintain its current weight. This deficit prompts your body to use stored fat for energy, leading to weight loss. However, it's important to create a healthy deficit that supports your overall well-being. Extreme calorie restriction (<500 daily calorie deficit) can lead to muscle loss, nutritional deficiencies, and metabolic slowdown. A moderate, sustainable deficit is key to long-term success.
The Thermal Effect of Exercise (TEE)
The Thermal Effect of Exercise (TEE) refers to the increase in caloric expenditure that occurs during and after physical activity. Unlike the Basal Metabolic Rate (BMR), which measures the energy your body needs at rest, TEE represents the additional energy your body demands when you engage in physical activities. This includes everything from structured workout routines to everyday movements like walking or even fidgeting.
Understanding TEE
When you exercise, your muscles require more energy to perform the movements, resulting in an elevated calorie burn rate. The intensity, duration, and type of exercise all influence how much energy your body expends. For example, high-intensity activities such as running, swimming, or cycling typically burn more calories per minute compared to lower-intensity exercises like walking or yoga. Additionally, high intensity physical activity with resistance is even more superior at burning more calories per minute compared to bodyweight movements like running, swimming, or cycling.
Post-Exercise Caloric Burn
An interesting aspect of TEE is the phenomenon known as Excess Post-Exercise Oxygen Consumption (EPOC), often referred to as the "afterburn effect." After you finish exercising, your body continues to consume oxygen at an elevated rate to restore itself to its resting state. This process involves replenishing energy stores, repairing muscle tissues, and removing metabolic waste products, all of which require additional energy. The more intense the workout, the longer and more significant the afterburn effect.
Factors Influencing TEE
Several factors can affect your TEE, including:
· Exercise Intensity: Higher intensity workouts lead to greater caloric expenditure both during and after exercise.
· Exercise Duration: Longer workout sessions increase total energy expenditure. Be aware however, that longer workout sessions generally equate to a lower intensity, which is then counterintuitive to increasing your TEE.
· Type of Exercise: Activities that engage multiple muscle groups and involve resistance (e.g., strength training, HIIT) tend to have higher TEE.
· Individual Characteristics: Age, gender, body weight, and fitness level can all influence how much energy you expend during exercise.
The Thermal Effect of Food (TEF)
TEF refers to the energy your body uses to digest, absorb, and metabolise food. It accounts for approximately 10% of your total daily energy expenditure. Different macronutrients have varying TEF values, with protein having the highest, followed by carbohydrates and fats. By including more protein in your diet, you can slightly increase your calorie burn and support muscle maintenance during weight loss.
The relationship between BMR, Physical Activity, TEE, TEF, and Body Composition
Let’s presume your BMR is 2000 calories per day, a typical example. If you continuously and regularly consume 2000 calories per day and not move too much, then your body will stay the same.
After performing physical activity and expending 500 calories, you will be in a calorie deficit. If you consume food afterward that amounts to 500 calories, then you’re back to 2000 calories.
If you perform physical activity amounting to 500 calories and consume 1000 calories before or afterward, then your net gain is 500 calories.
This is where it gets interesting.
The type of physical activity you perform makes a difference, the intensity at which you exercise makes a difference and the amount and type of food you consume before and after make a difference.
Exercise type
Exercising at high intensity with resistance positively influences your body composition. Put simply, strength training at high intensity can increase your muscle mass. Plyometric training, boxing, High Intensity Interval Training (HIIT) with light to medium weights are further examples of high intensity training with resistance. Furthermore, for muscle mass to occur, the your body must be in a net positive state for muscle growth to occur. Hence why we often talk about recovery shakes or protein shakes.
Exercise intensity
The harder you breath, the more calories you will burn compared to exercise of the same duration. Put simply, breath harder to burn harder. To maximise TEE for fitness and weight management, consider incorporating a mix of aerobic (medium intensity) and anaerobic (high intensity) exercises into your routine. HIIT training with light to medium weights is particularly effective for boosting TEE due to its combination of intense effort and varied movements.
Nutrition pre and post
Because protein demands the most amount of energy to metabolise, the TEF for protein is higher than for example carbohydrates and fats. Furthermore, our body is made up of approximately 20% protein and this nutrient is particularly essential when the goal is to improve body composition; decrease body fat and increase muscle mass. Maintaining a balanced diet rich in protein can support muscle maintenance and growth, further enhancing your metabolic rate.
This is of course not to say we don’t need the other macronutrients! Carbohydrates and fats are equally important for energy, for our hormone balance and for satiety, amongst other functions.
Body composition i.e. weight loss/gain
Body composition relates to the ratio of fat mass to muscle mass. An improved body composition, i.e. less body fat and more muscle, increases the BMR. This is why men can generally eat more calories than women and maintain the same bodyweight! Because men typically have a higher ratio of body fat to muscle mass, their BMR is higher, even when both parties are of the same bodyweight.
Best & Worst Case Scenario
In an ideal world when we talk about losing weight, what we mean is ‘improving body composition’. With the right combination of physical exercise and nutrition, positive body composition gains can be made in a relatively short period of time. In as little as 8 weeks it is possible to lose 8kg of mass (predominantly body fat) in a healthy and sustainable manner and without going to any extremes. This results in an increase in BMR, needing more calories at rest.
Conversely, it is also possible in as little as 8 weeks to lose 8kg of mass, of which is predominantly muscle mass. This results then in a decrease in BMR (needing fewer calories at rest) and often happens when we restrict our energy intake whilst doing predominantly low intensity exercise (walking, swimming, yoga). Exercises that don’t offer resistance.
To summarise, combining these concepts effectively can enhance your fitness results and maximise the efficiency of your efforts in the gym and the kitchen. By understanding and applying the principles of BMR, weight loss, body composition, calorie deficit, and TEF, you can achieve a balanced and successful approach to health and fitness.
Kudos to you for getting to the end of this lengthy blog!
Eske Dost