The Science of
Fat Loss

Over time, body fat decreases when you consistently expend more energy than you take in. Food quality, timing and diet style matter for health, hunger and adherence, but they work through this underlying balance, not around it.

TDEE is the energy you use each day. It includes your resting metabolism, digesting food, exercise, and everyday movement like walking and fidgeting. Calculators can only estimate it.

A deficit means eating less than your estimated maintenance. Larger deficits may produce faster initial weight loss, but they can also increase hunger, reduce training performance and be harder to sustain. A bigger deficit isn't automatically better.

The TDEE calculator shows an estimated weekly rate for each deficit option, using a simplified conversion. These numbers are estimates. Real-world weight trends often differ, especially early on when water and glycogen shift.

Use your average weight trend over several weeks as feedback, and adjust from there. Faster isn't inherently better. Pick a pace you can keep up while still training well.

Adequate protein can help preserve muscle during a deficit, and many people find it helps with fullness.

Resistance training gives your body a reason to keep muscle while you lose fat. Aim to maintain or progress performance where you can.

Everyday movement such as walking, taking the stairs and moving around can contribute meaningfully to energy expenditure. It's easy to adjust, and it may drift down without you noticing when dieting.

Day-to-day weight can swing with water, salt, carbohydrate intake, food in the gut and hormonal cycles. These swings aren't fat. Weekly averages, measurements and how clothing fits give a clearer picture than any single weigh-in.

Apparent plateaus are common. They can come from water retention masking fat loss, intake gradually creeping up, lower daily activity, or expenditure falling slightly as you get lighter. Give it a couple of weeks of consistent data before changing your approach.

• Spot reduction: training a body part doesn't specifically burn the fat over it.
• "Fat-burning" foods or supplements: none replace an energy deficit.
• Carbs at night cause fat gain: total intake over time matters far more than timing.
• You must do cardio: it can help, but it isn't required to create a deficit.
• Faster is always better: aggressive approaches are often harder to sustain.