Intermittent Fasting for Weight Loss: Beginner's Guide

If you have heard about eating patterns that restrict meal timing, you might be curious about intermittent fasting for weight loss. This beginner’s guide explains what it is, how it works, and whether it fits your lifestyle. Before starting, know your BMR using our BMR calculator – because even with fasting, total calories still matter.

What Is Intermittent Fasting?

Intermittent fasting is not a diet; it is an eating schedule. You alternate between periods of eating and periods of fasting. There is no restriction on what you eat, only when you eat.

Common methods include:

16/8 method: Fast for 16 hours, eat within an 8‑hour window (e.g., 12pm‑8pm)
5:2 diet: Eat normally for 5 days, restrict calories (500‑600) on 2 non‑consecutive days
Eat‑Stop‑Eat: 24‑hour fast once or twice per week

This guide focuses on the 16/8 method because it is the most sustainable for beginners. Consequently, many people find it easier to follow than constant calorie counting.

How Intermittent Fasting Aids Weight Loss

Intermittent fasting helps weight loss through several mechanisms:

Automatic calorie reduction – Shortening the eating window often leads to eating fewer total calories without conscious effort.
Improved insulin sensitivity – Fasting lowers insulin levels, which may increase fat burning.
Hormonal changes – Fasting boosts norepinephrine and human growth hormone, supporting metabolism.

However, the primary driver of weight loss remains a calorie deficit. Intermittent fasting is a tool to create that deficit, not magic. Therefore, you still need to know your TDEE. Use our TDEE calculator to find your maintenance calories.

Popular Schedules for Beginners

Here are three schedules ranked by difficulty.

Method	Eating Window	Fasting Duration	Best For
12/12	12 hours	12 hours	Very beginners, minimal change
14/10	10 hours	14 hours	Gradual adaptation
16/8	8 hours	16 hours	Most popular, effective

Recommended start: Begin with 14/10 for one week. Then progress to 16/8. This step‑by‑step approach reduces hunger and crankiness.

Example 16/8 schedule:

12:00pm – First meal (lunch)
3:00pm – Small snack
6:00pm – Dinner (finish by 8pm)
8:00pm start fast until 12:00pm next day

You sleep through most of the fast. Thus, many people find it surprisingly easy.

What Can You Drink During the Fast?

During fasting hours, you must consume zero calories to maintain the fasted state. Nevertheless, these beverages are allowed:

Water (still or sparkling)
Black coffee (no sugar, milk, or cream)
Plain tea (green, black, herbal)
Non‑caloric electrolytes

Avoid diet sodas – some research suggests they may still spike insulin. Similarly, avoid any creamer or sweetener. Stick to plain drinks.

How to Combine Intermittent Fasting with Calorie Tracking

This is the most common mistake. People think fasting means they can eat unlimited calories during the eating window. However, weight loss still requires a deficit.

Step‑by‑step:

Calculate your BMR using our BMR calculator .
Find your TDEE (maintenance calories) via our TDEE calculator .
Subtract 300‑500 for weight loss – this is your daily target.
Distribute those calories across 2‑3 meals within your eating window.

For example, a female with TDEE 2,100 wants to eat 1,700 calories for weight loss. She splits that into a 700‑calorie lunch and a 1,000‑calorie dinner – both nutritious and satisfying.

For a full explanation of deficit targets, see our guide on how many calories to eat to lose weight .

What to Eat During Your Eating Window

Because you have fewer meals, each meal must be nutrient‑dense. Prioritise:

Protein – crucial for muscle preservation (see how much protein per day to build muscle )
Fibre – vegetables, fruits, whole grains for satiety
Healthy fats – avocado, nuts, olive oil for hormones
Complex carbs – quinoa, sweet potatoes, oats for energy

Avoid processed foods, sugary drinks, and empty calories. They will leave you hungry and make fasting harder.

Example 16/8 Meal Plan (1,700 calories)

Eating window: 12pm‑8pm

12:00pm (Lunch – 600 cal):
150g chicken breast, 1 cup brown rice, 2 cups mixed vegetables, 1 tbsp olive oil
3:00pm (Snack – 200 cal):
1 apple + 1 tbsp peanut butter
6:30pm (Dinner – 900 cal):
200g salmon, 1 large sweet potato, large salad with avocado, 2 tbsp vinaigrette

Total: 1,700 calories, ~120g protein, ~50g fibre. This keeps her full and supports weight loss.

Benefits Beyond Weight Loss

Intermittent fasting has other potential benefits, although research is ongoing:

Improved insulin sensitivity (lower diabetes risk)
Cellular repair (autophagy)
Reduced inflammation
May support brain health

Nevertheless, these benefits are not guaranteed for everyone. Consistency and overall diet quality matter more.

Common Mistakes Beginners Make

❌ Breaking the fast with sugar – A fruit juice or sweet coffee spikes insulin and crashes energy. Break your fast with protein and fibre.

❌ Eating too little – Some people undereat because they cannot fit enough calories into the window. This lowers metabolism. Use our maintenance calories guide to avoid eating below BMR.

❌ Not drinking enough water – Fasting increases water loss. Dehydration causes headaches and fatigue. Drink 2‑3 litres daily.

❌ Giving up after a few days – Hunger is worst on days 2‑4. Push through; it gets easier. Your body adapts.

❌ Fasting while sick or pregnant – Not recommended. Consult a doctor first.

Who Should NOT Do Intermittent Fasting

Intermittent fasting is not for everyone. Avoid if you:

Are underweight or have an eating disorder history
Are pregnant, breastfeeding, or trying to conceive
Have diabetes (especially on insulin) – medical supervision required
Have low blood pressure or take medications that require food
Are a child or adolescent

When in doubt, speak with a healthcare professional.

How to Transition Back to Normal Eating

If you want to stop fasting, do not suddenly return to eating all day. Gradually extend your eating window by 1‑2 hours every few days. For example:

Week 1: 16/8
Week 2: 14/10
Week 3: 12/12
Week 4: Regular 3 meals

This prevents rapid weight regain and digestive issues.

Frequently Asked Questions

Will intermittent fasting slow my metabolism?
No, if you maintain a reasonable calorie intake. However, very low calorie intake (below BMR) during the eating window can slow metabolism. Therefore, never eat below your BMR. Learn why in how to increase metabolism naturally .

Can I exercise while fasting?
Yes, low‑intensity exercise (walking, yoga) is fine. For heavy lifting or HIIT, many prefer to exercise near the end of the fast or right after breaking it. Experiment to see what works for you.

Do I need to eat breakfast?
No. The belief that breakfast is essential for metabolism has been debunked. If you feel fine skipping it, intermittent fasting is perfectly safe.

How long until I see weight loss results?
Typically, 2‑4 weeks of consistent fasting with a calorie deficit. However, weight loss depends on your deficit size. For realistic rates, see our calories to lose weight guide.

Can I build muscle with intermittent fasting?
Yes, but it is harder because you must consume enough protein and calories in a shorter window. Consider a larger eating window (10 hours) or using protein shakes. Read how many calories to build muscle for strategies.

What is the difference between BMR and RMR? Does fasting affect them?
Fasting does not directly change BMR or RMR. However, chronic undereating does. For the distinction, see BMR vs. RMR .

Which BMR formula is used for fasting calculations?
Our BMR calculator uses Mifflin‑St Jeor, the most accurate. For the science, see BMR formula: Mifflin‑St Jeor vs. Harris‑Benedict .