Keto, intermittent fasting or calorie deficit?

Keto. Intermittent fasting. Paleo. Low carb. Carnivore. The amount of diets is overwhelming. Everyone has an opinion. Everyone has an anecdote. And everyone claims their approach is the best.

But what does science say? The answer is surprisingly simple - and at the same time frustrating for everyone hoping for a magic formula.

The only thing that really matters: calorie deficit

Every diet that works, works for the same reason: it ensures you consume fewer calories than you burn. That's it. There is no magical metabolic advantage of keto over intermittent fasting, or of paleo over simply eating less.

Hall et al. (2021) proved this in a rigorous, controlled study. Participants received two weeks of a ketogenic diet and two weeks of a low-fat diet, both with exactly the same calorie intake. The result? No difference in fat loss when calories were equal.

This is the most consistent result in nutritional science: calories determine whether you lose weight, not the distribution of macronutrients.

Keto: the facts

The ketogenic diet restricts carbohydrates to less than 20-50 grams per day. Your body switches to fat burning as its primary energy source and produces ketones.

Benefits:

• Many people experience less hunger due to the high fat and protein intake
• More stable blood sugar - no peaks and valleys
• Can be effective for people who struggle with portion control around carbohydrates
• Some people report more mental clarity

Drawbacks:

• Very restrictive - many foods are forbidden (bread, pasta, fruit, many vegetables)
• Difficult to maintain long-term
• Can negatively affect your athletic performance, especially during intense training
• Socially difficult - going out to eat or eating with others becomes a challenge
• The first 1-2 weeks often feel miserable ("keto flu")

The verdict: keto works if you stick to it. But most people don't stick to it. And that's the whole problem. Also read what science says about carbohydrates as friend or foe.

Intermittent fasting: the facts

Intermittent fasting (IF) is not a diet in the traditional sense - it's an eating pattern. The most popular variant is 16:8: 16 hours fasting, 8 hours eating. Other variants are 5:2 (5 days normal eating, 2 days very little) and OMAD (one meal a day).

Benefits:

• Simple - you don't need to count calories, just the clock
• Fewer meals often means automatically fewer calories
• Suits people who aren't hungry in the morning
• No foods are forbidden

Drawbacks:

• You can still eat too much in your eating window
• Can lead to overeating after fasting
• Not ideal if you train in the morning and want to eat afterwards
• Can be difficult for people with a history of eating disorders

Cioffi et al. (2018) analyzed 11 studies on intermittent fasting and concluded that IF is not superior to continuous calorie restriction for weight loss. The result is comparable - if total calorie intake is equal.

The verdict: IF is a fine strategy if it fits your rhythm. But it's not magic.

Simply eating less: the invisible winner

No fancy name. No book. No Instagram guru promoting it. Simply: know how much you need and stay below that.

Benefits:

• Maximum flexibility - you can eat everything
• Easy to adapt to your life, social occasions, seasons
• You learn portion awareness - a skill you take with you for the rest of your life
• Compatible with every training method

Drawbacks:

• Requires some knowledge of portions and calories
• In the beginning you might need to track what you eat
• Less "exciting" than a trendy diet - and that makes it less attractive

The big comparison: what does the research say?

Ge et al. (2020) published an extensive comparison of all popular diets. Their conclusion was clear: at 12 months there is no significant difference between diets, as long as the calorie deficit is comparable. Moreover - most diets show a relapse after 6 months, regardless of which diet it is.

The reason? Sustainability is the magic word. A diet that you maintain for 3 months and then quit loses to a slightly less "perfect" diet that you maintain for a year.

The best diet is the diet you actually stick to. Not the diet that promises the fastest results on paper.

The adherence factor

This is what it really comes down to. Adherence - in other words: how well do you stick to it? The less a diet disrupts your life, the greater the chance you'll stick to it.

Ask yourself these questions:

• Can I still do this in 6 months?
• Does it fit my social life?
• Do I still have energy for my training?
• Do I feel good about it, or am I constantly waiting for the moment it's "over"?

If a diet feels like a temporary punishment, then it is. And as soon as the punishment is over, the weight goes back up.

How much protein do you need?

Regardless of which eating pattern you choose, one thing is universal: make sure you get enough protein. Protein protects your muscle mass during weight loss, satisfies better than carbohydrates or fats, and costs your body more energy to process. Read here exactly how much protein you need per day.

My advice: start simple

You don't have to choose between keto, IF or something else. Start with the basics:

1. Calculate your calorie needs - your TDEE (total daily energy expenditure) minus 300-500 kcal for gradual weight loss
2. Eat sufficient protein - 1.6-2.2 grams per kilogram of body weight
3. Eat vegetables with every meal - for fiber, vitamins and satiety
4. Choose a structure that suits you - 3 meals, 16:8, 5 small meals, it doesn't matter
5. Be consistent - 80% good is better than 100% perfect for 3 weeks

No labels needed. No extreme rules. Just an approach that works in your life, with your schedule, with your preferences.

It may sound less sexy than "keto transformation in 30 days" - but it's what actually works long-term.