Rules of healthy diet: how to lose weight, how to gain muscle mass

The aim of the article: basic dietary rules and what to follow

The aim of this article is not to offer one specific and simple answer to the question of dietary modification for weight management and improved health. I will try to give a few examples, but the main purpose of the article is to present the basic rules of diet so that the reader can get a handle on the subject and know what to trust and what to avoid.

Unfortunately, there is a lot of confusion on the subject of diet, so no one can be blamed for not knowing what to follow in order to achieve their goals. Magazines, websites and TV programmes are full of diets, advice and recommendations, but rarely is it explained why a particular diet or advice is supposed to work.

If you want to change your eating habits so that they actually lead to achieving your goals and are sustainable in the long term, unfortunately you cannot avoid at least a brief study of metabolic processes, caloric balance principles and macronutrient ratios. At first glance this may sound scary, but in reality there are only a few of the most important rules of eating and it is these that I want to describe in this article.

Don’t believe (all) the articles on the internet and in magazines!

If you’ve ever searched the internet for tips and tricks on how to lose (or gain) weight, you know that the problem is not the lack of information available. Rather, the problem lies in overwhelming our minds with information and advice that is at best inaccurate and misleading, at worst completely wrong.

Unfortunately, healthy eating and dieting is a topic on which almost everyone has an opinion, but very few people have real expertise and knowledge in this area. I certainly can’t put myself in the position of an expert. I have plenty of experience and knowledge about nutrition in the context of fitness, but I am not a doctor or a trained nutritional therapist. Therefore, I would urge everyone to consult their doctor before making any major dietary changes.

Since diet and its impact on human health is a topic that encompasses chemistry, biology, and physics, I hope it is obvious that this is a serious science that is certainly no more trivial than other exact disciplines.

So, if you are listening to the (honest and well-meaning) advice of a neighbor, grandmother, or random commenter on an internet forum, imagine if you were listening to advice from these people about fissioning the nucleus of uranium or comments on the architectural plan for your dream house.

It doesn’t necessarily mean that the advice and opinions disseminated are bad, but they may only be appropriate for someone, for a particular situation or purpose, they may work well in the short term but be inappropriate in the long term, etc. The less informed we ourselves are on the subject, the more important it is to be critical and careful about the sources of information we consume.

Although the subject of nutrition is incredibly complicated and many questions do not even have a clear answer yet, the basic principles of diet are quite simple, so fortunately you don’t have to study for years to get advice for the purposes of weight management and improved health.

The importance of calorie intake and expenditure for weight management

The good news is that the only factor that determines weight gain or loss is caloric balance. What really matters is how many calories you take in and how many you put out in a day. The bad news is that there is no way to magically bypass this formula, and that calorie intake and expenditure is not as simple a matter as it might seem.

The body needs energy (calories/kilojoules) for basically all of its processes. For muscle contraction (including the heart and blood circulation), for digestion, for the production of many substances essential for life and health (hormones for example), for regeneration and growth, for perception and thought, etc.

Since one of the strongest instincts is the instinct for self-preservation, the human body behaves very conservatively or works tooth and nail to conserve precious energy. This means that as soon as we take in more calories than we consume, we quickly store them in reserves (mostly in the form of fat during inactivity, in muscle and fat during an active lifestyle).

There is an obvious reason for storing energy as fat – when there is nothing to eat, the body takes energy from stores. Nowadays, when (at least in the Western world) food is available to us in almost any quantity and quality, this life-saving mechanism unfortunately turns into a double-edged weapon. What once helped us to survive is now, in extreme cases, literally killing us.

The unfortunate fact is that we still have the original primal instincts combined with incredibly advanced and efficient technology, which means that we are living in extreme material abundance to which our biological shells are simply not adapted.

So if we want to adjust our weight in any way, we need to calculate how many calories we realistically need and adjust our diet accordingly.

Basal metabolism

The first and for most people the main item of caloric expenditure is the so-called basal metabolism. Basal metabolism is the energy requirement that the body uses for all its functions except exercise. In other words, basal metabolism is the amount of energy the body must take in if it is to maintain exactly the same weight with minimal physical exertion.

It’s important to remember that even if you were lying in bed all day, there are still a number of energy-consuming processes going on in the body, such as digestion, circulation, respiration, the formation of new cells, and so on. If we don’t take into account physically extremely active individuals such as elite athletes, basal metabolism accounts for approximately 70-95% of daily calorie consumption!

Unfortunately, basal metabolism varies from person to person due to many factors. The main ones include body weight (especially the amount of muscle mass), age, genes, and physical fitness (an athlete burns more calories even when idle). Since many variables enter into the formula, everyone has to calculate their own caloric needs (and then adjust the results).

Calculators and energy balance – how to gain or lose weight?

Calculating calorie consumption is a complex and individual matter. I’m sure you know cases of people who can eat whatever they like without gaining weight, while someone else eats sparingly and still fails to lose weight.

But none of this is magic or fate, it’s just a matter of adjusting the right amount of calories for individual needs and the laws of physics will do their thing! So how do we know what our daily calorie intake is and how much we should eat to lose or gain weight?

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In my opinion, there are two options. The first way is less accurate but easier, the second is accurate but costs more effort:

  • Every day, stand on the scale (at the same time) and it will be your compass. You’ll adjust your diet as you need to, and then you’ll honestly watch the needle of your personal scale every day. You’re following a long-term trend, so you’re not concerned about suddenly jumping a pound the morning after a big party or dropping a pound because you didn’t have time to eat because of work! You care about whether you drop, rise, or have the same numbers after a few weeks. Then you can adjust your diet according to that tendency.
  • You calculate an estimate of your calorie consumption and eat enough each day to have a slight deficit (if you want to lose weight) or a slight surplus (if you want to get stronger). So each day you need to calculate how much of what you eat. At first, this seems completely impossible because reading each package, weighing the portions, and calculating the value of each snack takes time and effort. Very soon, however, you will learn the values by heart and your estimate will be accurate enough that you will only have to weigh and examine new ingredients that you haven’t counted yet.

Whether you choose to count calories or not, it’s still helpful to at least have an idea of how many calories someone needs. The recommended daily allowance for an adult is two thousand calories. This number is pretty useless, but it’s a good start. So the average adult’s diet is probably around 2,000 kcal per day.

There are also several factors to take into account. One factor is current weight and especially current muscle mass. The bulkier a person is, the more calories they need to maintain their weight. It may seem strange, but even a person who is very overweight needs a relatively large amount of food to lose weight, because they are eating a lot of mass.

So it follows from this principle that men need more calories on average than women (they usually weigh more and have more muscle mass). Age may also play a role, as metabolism usually slows down at older ages. Conversely, an immature person consumes more energy (due to growth, etc).

The final factor for estimating basal metabolism is genes. Some people are naturally lean, others gain weight easily, but most people are somewhere in between, not at the extremes. Based on your own experience, you know best which side of this spectrum you fall on, and you should take that into account when determining your daily caloric intake.

In addition to the basal metabolic rate that keeps us alive and healthy, physical activity needs to be factored into caloric expenditure. This is by no means just about hard training, but also about how much you walk each day and whether you are sedentary or, conversely, move around a lot at work. For most people with sedentary jobs this will be a pitifully small number (compared to basal metabolic rate), but if you work in construction, for example, or workout every day, it will already be a noticeable amount of energy.

So how do you realistically calculate your caloric needs to reach your goals? I’ve deliberately avoided specific numbers as they will vary greatly from person to person, but I’ll try to at least give some guidelines. For example, you can try one of the many free online calorie calculators (for example: ) or consult a nutritional therapist. You can also eat exactly as you are used to for a week , but add everything up and then try adding or subtracting 20-30% depending on which direction you want to move in.

Why do diets usually not work and how do you get used to healthy eating?

My intention is definitely not to criticize all diets. Many diets have a head and a heel, are sensibly devised and set up, and if one follows them, they work. The problem, however, is the approach itself. The term diet implies that it is an exceptional, time-limited condition. If you return to your original regimen after the diet is over, you will gradually return to your original physical state as well.

That’s why I don’t really like fast and extreme diets that work (you do manage to lose weight), but after you finish them, you return to your original shape at the same speed. With longer and more sensible diets, you at least have a chance to build new eating habits and maybe keep some of them after you’re done.

Unless you need to quickly adjust your weight with a very specific goal (for example, to fit into a weight class for a match), I think the right approach is a slower, more persistent effort to change your habits. Also, being overweight doesn’t come out of nowhere in a week, but is the result of long term dietary mistakes.

The specific food choices, timing of meals, type of physical activity, and certainly not the use of supplements is not the deciding factor. The decisive factor is always discipline, i.e. following the rules we have set for ourselves. There is no way around it. If you want the results of your efforts to last, you must never stop trying.

It follows that an appropriate change in eating habits is one that you can stick to. Some people have no problem completely changing their lifestyle from one day to the next and never stopping, but such people are in the minority. For most people, changing habits is difficult and uncomfortable, so you only need to take the steps that you know you can stick to.

It’s perfectly fine to start by cutting out all sugary drinks, for example, or reducing your alcohol consumption to two days a week. The moment this change becomes your routine (you’re no longer tempted by cola or the pub), you can make another adjustment. Success is always a long haul run that you take one step at a time, not one leap at a time.

Macronutrients and their importance for the body

Looking at more specific aspects of diet, another essential aspect is determining the appropriate distribution of macronutrients.

So far we have only talked about the amount of calories, which is the top priority, but almost as important is the form in which you consume these calories.

A glass of Coke and a bowl of Caesar salad may contain the same amount of calories, but have vastly different nutritional values. We need to give our bodies everything they need to function healthily in our diets, otherwise we may lose weight, but we may also cause ourselves a host of other health problems.

A meal consists (in simplified terms) of three macronutrients, which I will try to describe very briefly:


Protein (protein) is an essential building material for the body that is needed for growth, recovery of injured and tired muscles (or muscle mass gain), bone and joint health, and many other purposes (hemoglobin production, etc.). One gram of protein is 4 kcal, but the conversion of protein to energy is relatively disadvantageous, which means, among other things, that protein is the least fattening.

Eating enough protein is essential for health, eating a lot of protein has many benefits, and eating too much protein in the long term, while potentially dangerous, is very rare. In my coaching experience, I have yet to meet anyone who consumes an unhealthy amount of protein.


Carbohydrates are primarily a source of energy. The body generally processes them easily and can use the energy quickly and efficiently, but this has its drawbacks as well. If you don’t use the energy, it gets stored (see above), and because it’s processed quickly, carbohydrates also make you hungry more quickly. One gram of carbohydrate also equals 4 kcal, but unlike protein, almost every person who struggles with excess weight eats too much carbohydrate.

Strictly speaking, there is no need to ingest carbohydrates because the body can make them through ketosis, but it is definitely not recommended to eliminate them from the diet for long periods of time. Reasonable carbohydrate restriction is usually good for weight loss, but extreme restriction causes fatigue and can even slightly impair concentration and thinking (the brain uses up a lot of glucose).


Fats are a source of ‘slower’ energy and are also essential for some important body processes, such as hormone production or digestion of fat-soluble vitamins. Therefore, we can reduce their intake, but we must never completely exclude them from our diet.

One gram of fat represents 9 kcal, which is the main reason why fats were once demonised and the prevailing opinion was that fats were the main cause of obesity. This theory was disproved some time ago. Although fats are the most calorically dense, they release energy more slowly, not in bursts like carbohydrates. Another advantage is that fats, especially when combined with protein, keep us fuller for longer, so hunger doesn’t return as quickly as when we eat a packet of biscuits.

Setting the optimal ratio of protein, fat and carbohydrates

Now that we know roughly what each macronutrient is important for, we need to decide in what proportions to include them in our diet. Personally, I always start by determining the amount of protein, as it is essential whether you want to lose weight or gain muscle mass.

Photo: Pixabay

As always, opinions vary, but 1.4-2 grams of protein per kilogram of body weight per day is cited as optimal. The more active a life you lead, the closer this number should be to the upper limit.

A naturally slim young boy who does a lot of sport and wants to put on weight will certainly not go wrong if he puts on 2 grams per kilogram of his weight. Someone who does not play sports and does not want to gain or lose weight will be fine with the lower limit, but even such a person will not make the mistake of eating more protein.

When deciding on the number of grams of protein, multiply the grams by four (1 g = 4 kcal) and subtract the resulting number of calories from the calorie intake. The rest of the calories must be supplemented with fats and carbohydrates.

This is more a matter of personal preference, but as mentioned above, for health reasons we cannot limit fat to more than 15% of our daily calorie intake (and 15% is already very low!). In general, it can probably be recommended that people who want to lose weight eat more fat at the expense of carbohydrates, while people who are gaining muscle mass may prefer to use carbohydrates as energy for strength training.

To illustrate, I’ll give two hypothetical examples:

  • Honza has been working in an office for the last 10 years, commutes by car, and has gained 95 kg (at an average height of 175 cm) due to his sedentary job and his fondness for sweet desserts. He does not like this and decides to adjust his diet. He calculates that his daily consumption is 2000 kcal, so he sets his intake at 1700 kcal so that he will have a deficit, but at the same time the deficit will not be so significant that he starves and slows down his metabolism. At 95 kg, he sets his protein intake at 140 g, which means he has 1140 kcal left for carbohydrates and fat. Since sweets are a stumbling block for him, he decides to prioritise fats, so his final plan looks like this -1700 kcal divided into: 140 g protein, 80 g fat, 105 g carbs. In practice, this means that he will have to reduce his portions of side dishes (pasta, pastries, rice, dumplings…) and limit his sweet to occasional biscuits. On the other hand, he can have the occasional fattier meat (with a big bowl of salad instead of the usual chips) and he doesn’t have to deny himself cheese, which is high in calories but not carbohydrates.
  • Marie is an enthusiastic rugby player who gives her all at every training session, but she worries that she has always been thin, so she has less strength than her teammates and has trouble defending the ball. She only weighs 60kg but has had a fast metabolism since birth and trains hard five times a week. So she calculated that she consumes 2300 kcal per day (which is a lot for a petite girl) and set her intake at 2700 kcal to maintain her excess and gain mass. Because of training she needs a lot of protein, so she chooses 130 g per day. This is even more than is needed for her current weight, but Marie intelligently expects to gain bulk and with that her need for protein will increase. Since she needs quick energy for training and also doesn’t like fatty foods, she will prefer carbohydrates to fats. The result is the following plan -2700 kcal divided into: 130 g protein, 90 g fat, 342 g carbohydrates. The next time she sits down to eat with her teammates after a workout, her friends roll their eyes at her lunch consisting of garlic sandwiches, steak with a mound of potatoes, and apple strudel. They may tap their foreheads, but the coach smiles and compliments her.

Micronutrients (vitamins and minerals) and their impact on health

At this point, we can have a decent idea of what a diet that will lead us to the goal that everyone has set for themselves might look like. However, in addition to macronutrients, the diet also contains important micronutrients, i.e. vitamins and minerals. There are a lot of them, so we will not go into describing them and just say that it is necessary to take in enough of them so that all the biochemical processes in the body can run properly.

The good news is that the vast majority of people in Western civilization are not deficient in any of the micronutrients. If you eat a varied diet and don’t skip any food category (meat, vegetables, grains, legumes…), there is a high probability that you are not deficient in any vitamin or mineral.

Your doctor should be able to tell you if you are deficient in any of the vitamins, so if you think you are lacking something (for example, frequent cramps may mean you are deficient in minerals such as magnesium, sodium, etc.), talk to your doctor and don’t look for the answer on the internet!

A problem can arise if you have somehow severely restricted your food intake. Whether it’s allergies, a weak stomach, or a personal decision, you need to be very careful about which micronutrients you may be missing due to restricting. We can find suitable substitutes for almost all foods , and in the worst case, we can replace the missing elements in pill form (which is not optimal, but it is better to take a vitamin in the form of an artificial powder than not at all).

To give just one example:

  • Peter has decided to stop eating all animal products. He consulted his doctor, who did not refuse him this choice, but warned him of some substances that he might be lacking or deficient in a purely plant-based diet. Being conscientious, Peter did not take the warnings lightly and followed the advice. He gets enough protein and iron from legumes, cereals, nuts and seeds. He gets vitamin D from mushrooms and by being outdoors frequently and happily, so he is regularly exposed to sunlight. As for vitamin B12, he sprinkles nutritional yeast on his hot meals, but prefers to take a B12 tablet from time to time just to be on the safe side.

Long-term sustainable monitoring of diet and body weight

Since dietary modification should be permanent, not a blip, we not only need to set boundaries that we can stick to, but we should also not worry about being able to maintain our diet completely.

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If ice cream is a nice end to a tiring day, it’s worth finding a place for it in your diet. It’s much better to have a slightly looser regimen and stick to it than to have an extremely strict regimen that we don’t follow.

Incorporating foods or snacks that we like but don’t fit the goal we’ve set can be done in a variety of ways, with a different way suiting everyone.

For example, we can allow ourselves a small piece of sweet each day that fits into our plan. That is, we treat ourselves every day, but only in a way that doesn’t disrupt the established pattern of caloric intake and macronutrient distribution. For some, this is the ideal solution because they get their fill every day, while for others it’s a disastrous plan because they can’t stop at two cookies and always eat the whole package.

Another possible approach is to have a stricter plan but indulge in any cravings one night a week. That way you can enjoy your meal to the fullest while taking a break from weighing portions, counting nutritional values, etc. for at least a little while. The disadvantage is obvious – if you are a big eater and tend to overeat, you can load up 2500 kcal in one evening, which will significantly disrupt your overall plan.

Whatever your approach, you need to enjoy yourself at times and not beat yourself up. This is also true in hindsight when you failed to stick to the plan because of a holiday feast or celebration with friends. Everyone makes mistakes and the past can’t be changed, so regrets only add to your stress and spoil your mental well-being. After a mistake, just get back on track and merrily move on.

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