Nutritionist explains What every diet fails to tell you - and how to really lose weight

Whether keto, low carb or intermittent fasting - hardly any diet delivers what it promises. Nutritionist Dr. Riedl explains why the body often doesn't play along and which strategies work in the long term.

Mr. Riedl, why do so many people fail to lose weight?

Most people don't fail because they don't want to, but because they misjudge their bodies. Losing weight is not just a calorie game. The liver, intestines, muscles, fatty tissue and hormones all work together. If you ignore this, you quickly get the feeling that your body is working against you - when all it's showing you is that something is out of balance. Then there's impatience: little often happens in the first few weeks and many people stop right then, even though the best progress often comes afterwards.

What other mistakes are there?

Many people resort to radical solutions: Mono diets, light products or appetite suppressants. This sounds logical, but is largely counterproductive. You lose muscle mass, reduce your energy consumption and end up with the yo-yo effect. Light products sometimes even contain more sugar, and appetite suppressants can also be dangerous.

What do you think about intermittent fasting?

Intermittent fasting can be a good start for many people. Longer breaks between meals stabilize blood sugar levels, reduce cravings and the body draws more on fat reserves. However, the decisive factor is what is eaten during the eating phases. If you overcompensate, you will lose the effect. Intermittent fasting is only suitable as a long-term solution if it is combined with a balanced diet.

What do you think about food combining - i.e. strictly separating proteins and carbohydrates?

The basic idea of food combining is scientifically untenable. Our body is able to digest mixed meals without any problems. When people lose weight on a food combining diet, it is usually because they automatically eat fewer calories and avoid more processed foods - not because of the separation of nutrients. In the long term, the concept is often complicated and only suitable for everyday use to a limited extent.

Low carb is considered by many to be the classic diet. And rightly so?

Low carb can certainly make sense - especially for people with insulin resistance, prediabetes or severe hunger attacks. Fewer carbohydrates often mean more stable blood sugar levels and better satiety. It becomes problematic when too much meat and animal fat ends up on the plate or entire food groups are omitted. Moderate variants are much more sustainable than extreme forms.

And what about the ketogenic diet - particularly strict but effective?

Ketogenic diets can be very effective in the short term, for example in cases of severe obesity or type 2 diabetes. They often lead to rapid weight loss and improve certain metabolic values.

In the long term, however, they are difficult to maintain and involve risks such as nutrient deficiencies, increased risk of arteriosclerosis or unfavorable cholesterol changes. They should therefore be used for a limited time, if at all, and with medical supervision.

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Is there one diet that is superior to all others?

No. None of these diets is clearly better than the others in the long term. The initial success is almost always due to a reduced calorie intake - not a "magic" diet principle. The decisive factor is whether a diet is suitable for everyday use, makes you feel full and can be maintained in the long term.

Your conclusion on the diet hype: Is there really one better diet - or is it all just marketing?

The crucial question is not which diet is the best, but which diet suits your everyday life and body. In the long term, studies show that the results of different diets largely converge after about a year. The initial success is almost always due to eating less bad food and more healthy food such as vegetables - not because of a specific diet principle. The real problem is therefore not so much the individual diet, but the principle of dieting itself.

Lasting success comes from a balanced, flexible diet that fills you up, is suitable for everyday life and does not involve extreme prohibitions.

Are there diets that are unsuitable for some people?

Yes, diets that cause constant hunger, demand strict prohibitions or do not fit in with our lives almost always fail. The body reacts with more hunger and more efficient fat storage. A diet that fills you up and can be flexibly adapted is sustainable.

Many people say: My metabolism is simply slow. Is that true or is it an excuse?

There are differences, yes - but they can be explained. Muscle mass, age, hormones and eating habits all play a role. What many people call a slow metabolism is often a permanently high insulin level due to frequent snacking. The good news is that the metabolism can be influenced - through exercise, muscle building and stable meals.

Why is losing weight easy for some and extremely difficult for others?

It has little to do with discipline. Some start with a tailwind, others with a headwind. Hormones, stress, sleep, living environment and habits make a huge difference. People who have a lot of stress or sleep badly have a much harder time - even with the same diet. In addition, some people have a wasteful metabolism and lose weight better than the thrifty type. This is genetically influenced.

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How can you lose weight in the long term without constantly torturing yourself?

By eating enough. Lots of vegetables, sufficient protein, healthy fats and a moderate amount of carbohydrates. This prevents hunger pangs. It is important to keep changes small. Mini-habits work better than radical changes.

Is there a formula for success that works for almost everyone?

Yes, stable blood sugar levels, strong satiety and a simple three-meal structure. Few meals, no snacks, no bans. And changes according to the 20:80 principle - step by step, not perfect.

What do you mean by the 20:80 principle?

Every businessman knows that he makes 80% of his profit from his most important customers. In terms of eating, this means that if you know your two to five most important eating mistakes, you can achieve 80% success with these alone. I know patients who have lost 20 kilos by correcting just one mistake.

What advice do you have for people who have lost confidence after many diets?

Don't blame yourself. The method was wrong. The problem is almost never a lack of discipline, but a system that doesn't work biologically. The new start begins with letting go of diets, analyzing your mistakes, changing them, eating enough and regaining control with small steps. Confidence is built through initial successes.

And how much does sport help with weight loss?

Unfortunately, sport is only the little brother of weight loss. It is a good help. Nobody should think they can lose weight with sport alone. You have to do over an hour of intensive exercise to eat a cinnamon roll.

Are there more suitable types of sport to help you lose weight? How often per week?

I recommend weight training, which is more effective for weight loss than endurance because it increases muscle mass. This increases energy consumption - even at rest. An hour twice a week is ideal - preferably more.

How important is the right mindset?

Very important. If you focus on enjoyment and satiety rather than abstinence, you are more likely to stick with it. Losing weight shouldn't feel like a struggle, but like a calm transition.

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What helps with relapses?

Relapses are normal. They are not a defeat, they can happen. Sometimes due to a stress reaction of the body. The important thing is not to question everything, but simply to return to the next good meal and carry on.

What advice do you have for people who are completely overwhelmed when it comes to losing weight?

Just change one thing. For example, no more snacks between meals today. It's better to have them with your main meal. Or more protein for breakfast or start every meal with vegetables. Slowly increase to 500 g of vegetables per day. But don't overexert yourself and don't force yourself. Life should also be fun. Small steps have an immediate effect - and motivate you.

If you could only give one tip for 2026 - what would it be?

Ultimately, it's about stable blood sugar levels. Put simply: every meal should consist of vegetables, protein and good fats. And then don't change everything at once, but first look at where things are going wrong and improve them step by step. Not quickly, but in such a way that you can really keep it up. Incidentally, highly processed foods are not very healthy. They are one of the main reasons for obesity - especially those with sugar.

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