Intermittent fasting: the complete beginner's guide

Intermittent fasting (or IF) isn't a diet. It's an eating pattern that alternates fasting periods with eating periods. It doesn't tell you what to eat, but when to eat.

How intermittent fasting works

When you eat, your body uses glucose (sugar) as its main energy source. Insulin rises to store the surplus.

When you fast, insulin drops. Your body uses up its glycogen stores (sugar stored in the liver and muscles), then starts to tap into fat for energy.

This process typically kicks in after 12 to 16 hours of fasting. That's why most intermittent fasting protocols start at 16 hours.

The 3 main methods

16/8 method (the most popular)

• 16 hours of fasting, 8 hours of eating
• Example: first meal at noon, last meal at 8pm
• You skip breakfast (or dinner)
• For whom: beginners, most people

It's the easiest method to adopt. Concretely, you skip breakfast and eat normally between noon and 8pm. Most of the fast happens during your sleep.

5:2 method

• 5 normal days, 2 days at 500-600 kcal
• The 2 restriction days shouldn't be consecutive
• Example: Monday and Thursday at 500 kcal, the rest normal
• For whom: those who prefer to eat normally most of the time

Eat Stop Eat method

• 1 to 2 complete 24h fasts per week
• Example: dinner at 8pm, no food until dinner the next day at 8pm
• For whom: intermediate/advanced, not recommended to start

Science-backed benefits

1. Easier weight loss

Intermittent fasting helps you lose weight mainly by reducing your total calorie intake. By eating in a shorter window, you naturally eat less.

According to a 2020 meta-analysis, intermittent fasting leads to a weight loss of 1 to 8% of starting weight over 3 to 24 weeks.

2. Improved insulin sensitivity

Fasting cuts fasting insulin levels by 20 to 31%, which makes it easier to use fat as fuel and reduces the risk of type 2 diabetes.

3. Daily simplification

One less meal to prepare, one less meal to track. Intermittent fasting simplifies your eating day and your grocery shopping.

4. Better focus (after adaptation)

After 1-2 weeks of adaptation, many practitioners report better mental clarity in the morning, likely tied to elevated norepinephrine during the fast.

5. Cellular benefits

Fasting activates autophagy, a cellular cleaning process where cells recycle damaged components. This process is associated with longevity and prevention of certain diseases.

Practical guide: starting 16/8

Weeks 1-2: gradual adaptation

Don't jump straight from 3 meals to 16h of fasting. Progress gradually:

• Days 1-3: push breakfast back by 1h (9am instead of 8am)
• Days 4-7: push back by 2h (10am)
• Week 2: push back to 11am-noon

In 2 weeks, you naturally reach a 16/8 window without suffering.

What you can consume during the fast

• Water (still or sparkling) -- mandatory, drink a lot
• Black coffee (no sugar, no milk)
• Tea (no sugar)
• Bone broth (optional, if hunger is difficult)

Anything that contains calories breaks the fast. A latte = broken fast.

Planning your meals

With 2 big meals and 1 snack over 8 hours, here's an example at 1,800 kcal:

Noon - Lunch (700 kcal) Grilled chicken 200g + cooked rice 200g + vegetables + 1 tbsp olive oil

4pm - Snack (300 kcal) 0% fat cottage cheese 250g + 30g almonds + 1 fruit

7:30pm - Dinner (800 kcal) Salmon 180g + sweet potato 250g + mixed salad + 1 tbsp olive oil + 1 dessert

With Kalo, track your calories and macros during your eating window by sending your meals via WhatsApp. Make sure you hit your nutrition targets despite the reduced window.

Protein: even more important

In a reduced window, hitting your protein targets requires planning. Aim for at least 1.6g of protein per kg of body weight.

Tip: concentrate your protein on your 2 main meals (40-50g each) and your snack (20-30g).

Common beginner mistakes

1. Eating anything during the window

Intermittent fasting isn't an excuse to eat fast food and pizza for 8 hours. The quality of your food still matters. If you eat 3,000 kcal of junk food over 8 hours, you'll gain weight.

2. Not eating enough

Paradoxically, some people eat too little during their window, which leads to fatigue, muscle loss and cravings. Make sure to hit your maintenance calories (or moderate deficit if you want to lose).

3. Ignoring hydration

Morning hunger is often disguised dehydration. Drink 500ml of water as soon as you wake up, then keep drinking throughout the morning.

4. Fasting too long too fast

Jumping straight to 20h or 24h of fasting without adaptation is a recipe for failure. Start with 14h, then 16h, and only after several weeks consider extending.

5. Training fasted without adaptation

Fasted training is possible, but requires a 2-3 week adaptation. If you train fasted in the morning, start with light sessions and ramp up gradually.

Who should avoid intermittent fasting

Intermittent fasting is not for everyone. Avoid it if:

• You have a history of eating disorders (anorexia, bulimia)
• You're pregnant or breastfeeding
• You have type 1 diabetes (consult your doctor)
• You take medications that must be taken with food
• You're a minor (under 18)
• You have low blood pressure problems

When in doubt, consult a healthcare professional before starting.

Intermittent fasting and exercise

Fasted lifting

If you train in the morning after fasting since the night before:

• Take 5-10g of BCAA 15 min before training (optional)
• Keep loads heavy but reduce volume (fewer sets)
• Eat a high-protein meal within 2h after training

Lifting during the eating window

This is the ideal scenario. Place your session between your meals:

• Meal 1 (noon) -> Training (3-4pm) -> Meal 2 (7pm)
• Or: Meal 1 (noon) -> Snack (3pm) -> Training (5pm) -> Meal 2 (7:30pm)

Expected results

Results depend entirely on your total calorie deficit, not on the fast itself. Fasting is a tool to make the deficit easier, not a magic solution.

Conclusion

Intermittent fasting is an effective tool to simplify your nutrition and ease weight loss. The 16/8 method is the most accessible: skip breakfast, eat between noon and 8pm, and make sure you hit your calorie and protein targets.

Track your meals easily with Kalo during your eating window. A WhatsApp message is enough to know your daily calories and macros.