The Science of Losing Weight and Body Composition

One quick look at the world of social media nutritionists (different from a licensed dietician) will drop you into a world so saturated with diet and health advice that achieving weight and fitness goals seems simultaneously simpler and more complex than ever.

Hundreds say “just one trick will X”, while several other hundreds swear by their diets. So, it begs the question, who is right (and correct)?

There are multiple ways to make a sandwich, but all sandwiches require bread. Body composition and weight change are both dictated by a simple process agnostic to all diets, people just have different methods of approaching it.

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Understanding Why Weight Changes

The cornerstone of weight management is caloric balance. There are three primary states of change relative to caloric consumption:

1. Loss

2. Maintenance

3. Gain

These states are determined by your base metabolic rate (BMR) — the number of calories your body burns at rest. Your metabolic rate is determined by a combination of factors including current health, genetics, and body composition. Caloric intake above, below, or at your BMR rate leads to the following:

1. Caloric Surplus: Consuming more calories than your BMR results in weight gain.

2. Caloric Deficit: Consuming fewer calories than your BMR results in weight loss.

3. Caloric Balance: Consuming calories equal to your BMR results in weight maintenance.

Lifestyle choices, particularly exercise, significantly impact the movement between these states. Exercise increases the number of calories burned, boosting your metabolic rate as muscle mass increases. Thus, a comprehensive weight change approach involves both diet and physical activity.

Framework for Surplus, Deficit, and Maintenance

That means all the dieting influencers are right in their own ways regarding their special meals- provided they align with the fundamental principle of caloric balance. However, there is a difference between eating avocado toast and chicken breast during those diets.

Exploring Body Composition

Body composition, the ratio of muscle to fat in the body, is shaped by the types and quantities of macronutrients consumed, along with the level of physical activity performed. Dieting trends and fads tend to play with how bodies respond to macronutrient changes. That means the avocado toast will contribute to a higher fat composition because avocados have more fat.

However, macronutrients are finicky, like most things, they can be swapped and transformed. For example, even a high protein macro diet combined with a sedentary lifestyle will mean the majority will be converted to fat as stored energy. Diets like keto leverage how your body chooses which macro will be the primary source of fuel, switching from carbs to fats.

This view illustrates how lifestyle changes (being either sedentary or active) contribute to the states of change.

Lifestyle Affects on Caloric Intake

The Role of Exercise

Exercise is a critical component of body composition and weight management. Different types of exercise offer various benefits. Some examples include:

• Cardiovascular Exercise: Activities like running, swimming, and cycling increase heart rate and calorie burn, contributing to weight loss by enabling a caloric deficit and improved cardiovascular health.

• Strength Training: Weightlifting and resistance exercises build muscle mass, which in turn increases BMR and helps maintain a healthy weight. Muscle tissue burns more calories at rest than fat tissue, contributing to greater long-term fat loss.

And before anyone tells you otherwise, I’m looking at you fitness influencers, spot burning fat is a myth.

Spot reduction, or spot burning, is the idea that you can lose fat in specific areas of your body by targeting those areas with certain exercises. For instance, doing sit-ups to lose belly fat or leg lifts to slim down the thighs.

Despite its popularity, the concept of spot reduction is largely a myth, and here’s why:

Fat Storage and Mobilization:

• Body Fat Distribution: Fat is stored in adipose tissues throughout the body and is influenced by factors such as genetics, hormones, and overall body composition. Where your body stores fat can vary widely from person to person.

• Fat Mobilization: When the body needs energy, it mobilizes stored fat by breaking it down into fatty acids and glycerol, which enter the bloodstream and can be used by muscles and other tissues for fuel.

Hormonal Influence:

• Hormones: Hormones play a significant role in fat storage and mobilization. For example, cortisol can influence fat storage in the abdominal area, while estrogen affects fat distribution in the hips and thighs. These hormonal influences mean that fat loss patterns are systemic and not localized.

Numerous studies have shown that spot reduction is not possible. Fat loss occurs systematically, not locally. Only a caloric deficit will reduce fat (and weight!).

Other Influencing Factors

Exercise and diet are the core drivers for body composition and weight change. But under the hood, many more factors can influence these changes, including:

• Genetics: Genetic predispositions can affect metabolism, fat distribution, and muscle growth, making it easier or harder for some individuals to gain or lose weight.

• Hormones: Hormonal imbalances, such as thyroid disorders or insulin resistance, can impact weight management and body composition.

• Sleep: Adequate sleep is essential for metabolic health. Poor sleep can disrupt hunger hormones and increase the risk of weight gain.

• Stress: Chronic stress can lead to hormonal changes that promote fat storage, particularly around the abdomen.

• Age: Metabolism tends to slow with age, making weight management more challenging. Muscle mass also decreases with age, impacting overall body composition.

• Hydration: Staying hydrated is crucial for metabolic processes and can influence hunger and energy levels.

Food for Thought:

French essayist Jean Anthelme Brillat-Savarin wrote in his seminal work Physiology of Taste, “Tell me what you eat, and I shall tell you who you are.” While this is usually interpreted as a keen observation of what our cuisine choices reveal about us, there is also a literal perspective. The composition of your food eventually determines your body composition, and there’s something poetic about the ability to control what becomes a part of you through the food you eat. Ultimately a deeper understanding of these dynamics might offer more profound insights than adopting the latest diet trend.