What Are Calories and Why Do They Matter for Weight Loss?

What Are Calories?

If you’ve ever looked at a nutrition label or tracked your food intake, you’ve likely come across the term calories. But what exactly are they, and why do they play such a big role in weight loss?

Simply put, a calorie is a unit of measurement for the energy in food. Every time you eat, your body extracts energy from food to fuel your body and everything you do, from basic functions like breathing and digestion to physical activities like walking and exercising.

When looking for calories on nutrition labels, you might notice that energy is either shown as kilocalories (kcal) or kilojoules (kJ). They both measure energy in different units. If a label shows kJ, you can divide it by 4.2 to convert it to calories (e.g., 840 kJ ≈ 200 calories).

Where Calories Come From

The number of calories a food contains depends on its composition of protein, fat, and carbohydrates. These are known as macronutrients, and each provides a different amount of energy per gram.

• Protein = 4 kcal per gram
• Carbohydrate = 4 kcal per gram
• Fat = 9 kcal per gram

Because of this, foods higher in fat tend to be more calorie-dense than foods higher in protein or carbohydrates. For example, a tablespoon of butter (mostly fat) can contain more calories compared to a much larger serving of strawberries (mostly water and carbohydrate).

Understanding where your calories come from and how much your body needs is the first step in learning how to manage your weight.

Why Calories Matter For Weight Loss

Weight change comes down to energy balance, or in other words, calories in versus calories out. Your body requires a certain number of calories each day to maintain your weight.

• If you eat the number of calories your body requires each day, your weight stays the same.
• If you eat more calories than your body requires each day, the excess energy is stored as fat, leading to weight gain.
• If you eat fewer calories than your body requires each day, your body uses its stored fat for energy, resulting in weight loss. This concept is known as a calorie deficit, which is the foundation of weight loss.

In order to create a calorie deficit for weight loss, you need to know two things;

1. Your body’s daily energy requirements,
2. The number of calories you are consuming.

What Determines Your Daily Energy Needs

Your body is using energy at all times, even when you are resting. It needs energy to keep your heart beating, lungs breathing, brain working, and body temperature steady. This “resting” energy is the biggest slice of your daily use.

On top of that, you use extra energy when you move. That includes planned exercise like a run or a gym session, and everyday movement like walking to the bus, carrying groceries, cooking, cleaning, or even fidgeting.

Your body also spends a small amount of energy digesting and processing the food you eat.

These three components make up your total daily energy expenditure. When you create an account in the fatsecret app, we estimate your daily energy needs based on details like your age, sex, height, weight, and how active you are. To this, we apply a calorie deficit, which gives your Recommended Daily Intake (the number of calories you need to eat each day to be in a calorie deficit and lose weight).

How to Ensure You’re In a Calorie Deficit

The fatsecret app makes it easy to track your food and understand how many calories you're eating each day. By logging your meals, you can see the number of calories you’re consuming and whether you're staying within your target for weight loss.

Your fatsecret Recommended Daily Intake includes the necessary calorie deficit for weight loss. This means you’ll know exactly how much to eat each day to stay on track.

By logging your meals using fatsecret, you’ll have a clear breakdown of:

• The calorie content of each meal you log
• How much you've eaten so far in the day
• How many calories you have left to reach your goal

This makes it easier to stay accountable and make informed food choices that support your weight loss journey. By consistently tracking your food, you can make sure you’re not over or under-eating. You might even start recognizing patterns in your eating habits, helping you make healthier choices over time.

Key Takeaways

• Calories are the energy in your food.
• Weight change comes from energy balance. Eating the same amount of energy that your body uses helps you maintain your weight; eating more leads to gain, and eating less creates a calorie deficit and leads to weight loss over time.
• Tracking your food in the fatsecret app makes it easy to stay in a calorie deficit for weight loss. When you log meals, you’ll see the calories for each food and meal, today’s calorie total, and how many calories you have remaining for the day.