A common question among people trying to lose weight is: When does the body actually begin to burn fat on a diet? The truth is, the answer varies from person to person depending on factors such as starting weight, body composition, and the type of diet and exercise plan being followed.
Generally, the body starts tapping into fat reserves within the first few weeks of sticking to a structured weight-loss programme that combines healthy eating and regular physical activity, On average, the safe rate of weight loss is around 0.5 to 1 kg per week.
What Does Weight Loss Depend On?
Several factors influence how quickly and effectively the body loses fat, Many of these are outside an individual’s direct control, including:
- Gender: Men usually lose weight more quickly than women when following the same calorie controlled diet, This is because men typically have a higher muscle-to-fat ratio, meaning they burn 5–10% more calories at rest compared with women.
- Age: Weight loss tends to become more difficult with age, Over time, muscle mass decreases while fat mass increases, and the body’s calorie needs drop.
- Health conditions and medication: Certain medical issues or treatments can either slow down or speed up fat loss.
The Two Main Stages of Weight Loss
- Rapid Weight Loss Phase (First 4–6 Weeks)
In the early weeks, most of the weight lost comes from carbohydrate stores, water, and a small portion of fat, This stage often results in noticeable changes in body shape and clothing fit. - Slower, Sustainable Fat Loss Phase (After 6 Weeks)
Once the initial stores are depleted, the body shifts to burning more fat, The rate of loss slows but becomes steadier and more sustainable over time.
Diet Approaches: Keto and Intermittent Fasting
Research suggests that low-carbohydrate approaches such as keto or intermittent fasting may trigger faster initial weight loss, largely due to glycogen depletion and water loss, before transitioning into fat burning.
Post-Pregnancy Weight Loss
For women after childbirth, weight reduction tends to begin gradually in the first few weeks, However, the pace depends on several factors including delivery type, breastfeeding, and physical activity levels.
The Bottom Line
Doctors emphasise that weight loss is a journey requiring patience and consistency, There is no universal timeline for visible results, but maintaining a balanced diet alongside regular exercise offers the safest path to long-term fat loss and improved health.