Calories are often misunderstood, but they play a vital role in everything your body does – from breathing and thinking to moving and digesting. Here’s your essential guide to how calories work and what your body actually needs.
Calories Are Your Body’s Main Energy Source

Every movement, thought, and function relies on calories. They fuel your muscles, organs, and brain – and without them, your body simply wouldn’t run.
Kilojoules vs. Kilocalories – What’s the Difference?

Food energy is measured in both kilojoules (kJ) and kilocalories (kcal). Most people track kcal, commonly known as “calories,” but both units appear on food labels.
Quick Conversion Between Units

To convert energy: 1 kJ equals 0.239 kcal. And 1 kcal equals 4.2 kJ. Understanding this makes it easier to decode nutritional information.
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Caloric Value of Macronutrients

Different macronutrients contain varying amounts of energy. Fat is the most energy-dense:
- 1 gram of fat = 9 kcal
- 1 gram of carbohydrates = 4 kcal
- 1 gram of protein = 4 kcal
Daily Calorie Needs Depend on Weight

For those with a healthy body weight and average activity levels, a rough rule is 30 kcal per kilogram of body weight per day.
Overweight Individuals Require Fewer Calories

If your BMI is over 30, a lower guideline of 25 kcal per kilogram is more appropriate due to a slower metabolism and reduced energy needs.
Want to Lose Weight? Create a Calorie Deficit

Weight loss occurs when you consume fewer calories than you burn. A deficit of 500 kcal per day can lead to a weight loss of around 0.5 kg per week.
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Avoid “Empty Calories”

Snacks like candy, chips, and sugary sodas add up quickly and offer little nutritional value. Reducing these makes a big difference without cutting out food altogether.
Calorie Burn Also Varies With Activity

Your total daily energy burn depends on your metabolism and physical activity. Exercise, walking, and even standing up more can increase your daily burn rate.
Eat More Foods That Fill You Up

Fiber-rich foods like whole grains, legumes, and vegetables keep you full longer and stabilize blood sugar. They also support digestion and make calorie reduction easier to manage.
Low-Calorie Foods That Don’t Feel Like a Sacrifice

Healthy, satisfying foods that are naturally low in calories include:
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- Chicken breast
- Carrots
- Cauliflower
- Cucumbers
- White fish
- Mushrooms
- Light soft drinks
These can help you stay full without overshooting your calorie goals.
This article is based on information from Med24
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