A Beginner's Guide To Weight Loss

The Science Behind Weight Loss

At its core, weight loss follows a principle that sounds deceptively simple: consume fewer calories than you expend. This concept, known as a caloric deficit, is the foundation upon which all effective weight loss strategies are built.

"The first law of thermodynamics applies to human bodies just as it does to any physical system," explains Dr. Marion Nestle, professor emerita of nutrition at New York University. "Energy can neither be created nor destroyed, only transferred or converted."

Why Counting Calories Works

Physique athletes rely on calorie counting as their primary tool for achieving precise body composition changes. Their method works because it transforms scientific principles into a measurable, actionable daily practice. As an example, here's Chris Bumstead, the most celebrated bodybuilder of the modern era, on counting calories to get contest ready.

When you count calories, you're essentially conducting a personal energy audit. It's your body's version of a budget. By tracking what you consume and comparing it to what your body needs, you create awareness that can lead to informed nutritional choices.

Research consistently shows that people who monitor their food intake tend to be more successful at weight loss than those who don't. A 2019 study in the journal Obesity found that participants who tracked their food consumption were significantly more likely to lose weight and keep it off.

The Four Pillars of Energy Expenditure

To lose weight, you need to be in a caloric deficit. To be in a caloric deficit, you need to be intaking less calories than your body's total daily energy expenditure. Your body's total daily energy expenditure (TDEE) has four key components:

1. Basal Metabolic Rate (BMR): This represents the calories your body requires to maintain basic functions while at rest—keeping your heart beating, your lungs breathing, and your brain functioning. For most people, BMR accounts for 60-70% of their total energy expenditure.

2. Thermic Effect of Food (TEF): Digesting, absorbing, and processing food requires energy. Your body burns calories to break down what you eat, particularly protein, which has the highest thermic effect. TEF typically accounts for about 10% of your total energy expenditure.

3. Non-Exercise Activity Thermogenesis (NEAT): This encompasses all the calories burned through non-exercise physical movements—fidgeting, standing, walking to your car, doing household chores. NEAT can vary dramatically between individuals and can account for anywhere from 15-50% of total energy expenditure.

4. Exercise Activity Thermogenesis (EAT): This represents the calories burned during intentional physical activity and exercise. For most people, this accounts for about 5-10% of total energy expenditure, though it can be significantly higher for very active individuals.

   
   
   
   

Creating a Caloric Deficit

Understanding these components allows you to strategically modify them to create a caloric deficit:

• Reduce intake: The most direct approach is to consume fewer calories than your body requires.

  • It's important to emphasize that while exercise has many benefits, it is not the biggest lever in creating a caloric deficit. Plainly, it's a lot easier to skip 1 slice of pizza than to run 3+ miles.

• Increase BMR: While largely determined by factors like age, sex, and genetics, building muscle through resistance training can modestly increase your BMR.

• Maximize TEF: Consuming adequate protein (typically 0.7-1 gram per pound of body weight) can slightly increase calorie burn through digestion.

• Boost NEAT: Simple changes like taking the stairs, parking farther away, or implementing standing breaks can significantly increase daily calorie expenditure.

• Incorporate EAT: Regular exercise, particularly a combination of cardio and strength training, can increase calorie burn and preserve muscle mass during weight loss.

Calculating Your Personalized Calorie Targets

Now that we understand the science, let's translate it into practical numbers you can use to guide your weight loss journey.

Finding Your Maintenance Calories

The first step is determining your maintenance calories—how much energy your body needs to maintain its current weight. The Mifflin-St Jeor equation is widely regarded as an accurate formula for estimating basal metabolic rate:

For men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

For women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

To convert this to maintenance calories, multiply your BMR by an activity factor that reflects your typical daily movement:

• Sedentary (little or no exercise): 1.2

• Lightly active (light exercise/sports 1-3 days/week): 1.375

• Moderately active (moderate exercise/sports 3-5 days/week): 1.55

• Very active (hard exercise/sports 6-7 days/week): 1.725

• Extra active (very hard exercise, physical job or training twice a day): 1.9

For example, a 35-year-old woman who weighs 68 kg (150 lbs), stands 165 cm (5'5") tall, and is moderately active would calculate:

BMR = (10 × 68) + (6.25 × 165) - (5 × 35) - 161 = 1,374 calories Maintenance calories = 1,374 × 1.55 = 2,130 calories per day

Setting Your Weight Loss Target

Research suggests that a moderate caloric deficit promotes sustainable weight loss while minimizing muscle loss and metabolic adaptation. A deficit of 500 calories per day theoretically yields about one pound of weight loss per week (since 3,500 calories roughly equals one pound of fat).

Using our example above, this woman might set her daily calorie target at: 2,130 - 500 = 1,630 calories per day. For most people, a deficit of 15-25% below maintenance calories is both effective and sustainable:

• Conservative approach (15% deficit): 2,130 × 0.85 = 1,810 calories

• Moderate approach (20% deficit): 2,130 × 0.8 = 1,704 calories

• Aggressive approach (25% deficit): 2,130 × 0.75 = 1,598 calories

Remember that these calculations provide estimates, not exact figures. Your actual needs may vary based on individual factors, and adjustments may be necessary as you observe your body's response.