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Beginner's Guide to Calories and Macros

Understanding the fundamental concepts of nutrition is the first step towards achieving your fitness goals. This guide covers everything you need to know about calories, macronutrients, and practical tracking.

1. Introduction to Energy Balance

The Golden Rule

Fat loss revolves around Calories In / Calories Out (CICO), which is based on the laws of thermodynamics.

At its core, weight management is a game of Energy Balance. This is the continuous relationship between "energy in" (calories you consume) and "energy out" (calories you burn). While intake is simply the food you eat, your output is more complex—influenced by your metabolic rate, physical activity (both exercise and daily movement), and body composition.

  • Caloric Surplus: Eating more calories than you burn leads to weight gain.
  • Caloric Deficit: Eating fewer calories than you burn leads to weight loss.
  • Maintenance: Eating roughly the same amount as you burn maintains your current weight (TDEE).

It's important to note that your "Calories Out" isn't just about gym sessions. It includes your Basal Metabolic Rate (BMR)—the energy needed just to keep you alive—along with the calories burned digesting food (TEF) and all your non-exercise movement (NEAT). Even having more muscle mass increases your daily burn!

The Mathematics of Weight Change

Caloric Balance = Calories Consumed - TDEE

(TDEE = BMR + TEF + NEAT + EAT)

Calculate your TDEE now
  • Surplus of ~3,500 kcal = 1 lb (~0.45 kg) of weight gain
  • Deficit of ~3,500 kcal = 1 lb (~0.45 kg) of weight loss

2. Understanding Macronutrients

Pixels make up a picture; macros make up your calories. There are three main macronutrients, and each plays a unique role in your body:

Protein

4 Calories per gram

Essential for building and repairing tissues, including muscle. It also helps you feel full.

Carbohydrates

4 Calories per gram

While carbohydrates are the preferred fuel for the brain and high-intensity exercise, at rest and during low-intensity activities the body relies more on fat oxidation.

Fats

9 Calories per gram

Crucial for hormone regulation, supporting cell membranes, and absorbing fat-soluble vitamins (A, D, E, and K). They provide a dense source of long-lasting energy.

3. How to Weigh Your Food

Estimating portion sizes is notoriously inaccurate. To truly know what you're eating, a digital food scale is your best friend.

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  1. Place your plate or container on the scale.
  2. "Tare" or "Zero" the scale so it reads 0.
  3. Add your food item and record the weight (in grams or ounces).
  4. Log it in your tracking app exactly as weighed (e.g., "Chicken Breast, Raw" vs "Chicken Breast, Cooked").

Tip: While weighing raw is standard, consistency is key. It is acceptable to track cooked weights as long as you use the corresponding "cooked" entries in your nutrition database. As the USDA notes, cooking significantly changes food weight (mostly water), so simply ensure your log matches your method (e.g., if you weigh it cooked, log "Chicken Breast, Cooked").

Scientific References

Additional Resources:

Beginner's Guide to Calories and Macros | Calorie Lab | Calorie Lab Guides