Losing Weight Without the Imbalances: The Risks of Not Cutting Out Nutrients

Many quick-weight-loss diets are built on the simple promise that simply eliminating one group of nutrients will cause the excess weight to "dissolve on its own." This is how the "fat-free," "carb-free," or nearly "protein-free" diet fads work. In reality, the body is far more complex. Proteins, fats, and carbohydrates perform different functions, and abruptly eliminating them, especially completely, inevitably impacts health. [1]

Modern research shows that weight loss is possible with a variety of diets: low-fat, low-carb, or balanced. The key factor isn't the "demonization" of a single macronutrient, but the overall calorie deficit and the duration of adherence. When a person eliminates an entire food group, calorie intake does drop sharply—but so does the intake of vitamins, minerals, fiber, and essential fatty acids. [2]

Furthermore, extreme restrictions are almost always poorly tolerated psychologically. In practice, strict prohibitions lead to obsessive thoughts about food, breakdowns, and weight fluctuations. Recent data link aggressive low-calorie diets and unilateral dietary restrictions with increased depressive symptoms, sleep disturbances, and increased fatigue, especially in overweight people. [3]

It's important to understand that any one-sided diet has a price. Cutting out fats affects hormones and the nervous system, an extreme carbohydrate deficiency interferes with normal brain and thyroid function, and a lack of protein destroys muscle and slows metabolism. In the long term, such "diets" not only fail to solve the problem of excess weight but also increase the risk of chronic diseases. [4]

The purpose of this article is to calmly examine the dangers of extremes, what major studies show, and how to organize your diet so that you can lose weight while maintaining healthy bones, muscles, heart, and psyche.

Table 1. Why “cutting one macronutrient” is tempting, but doesn’t work well.

Idea	Why does it seem attractive?	What's the problem?
Complete rejection of fats	Fats are high in calories, which means “remove the fat and the kilos will go away” [5]	The intake of fat-soluble vitamins and essential fatty acids decreases, and hormonal balance is disrupted.
Complete elimination of carbohydrates	“Carbohydrates turn into fat, so they need to be eliminated” [6]	The brain suffers, performance decreases, the load on the kidneys and liver increases, and the range of foods is limited.
Severe protein restriction	“The main thing is to remove calories, protein also has calories” [7]	Muscles are destroyed, metabolism slows down, strength and exercise tolerance decrease.
Strict low-calorie diet	“The less I eat, the faster I lose weight” [8]	Deficiencies of multiple nutrients, worsening mood, breakdown and rapid weight gain

The role of proteins, fats and carbohydrates in the body

Protein is the building block for nearly every structure in the body: muscles, bones, skin, the immune system, enzymes, and hormones. Adequate protein intake maintains muscle mass, even when calories are reduced. Protein promotes a feeling of satiety, helps maintain weight after weight loss, and reduces the risk of sarcopenia in older adults. Chronic protein deficiency forces the body to "eat" its own muscle to maintain vital functions. [9]

Fats are more than just a source of energy. They are essential for the synthesis of sex and steroid hormones, the absorption of fat-soluble vitamins A, D, E, and K, the formation of nerve cell membranes, and the normal functioning of the immune system. Polyunsaturated fatty acids, especially omega-3s, play a key role in regulating inflammation and protecting the cardiovascular system. Complete or near-complete elimination of fats from the diet leads to deficiencies of these substances and hormonal imbalances. [10]

Carbohydrates are the primary and most convenient source of energy for the brain, nervous system, and muscles. Glucose is essential for the normal functioning of the cerebral cortex and numerous hormonal and metabolic processes. When consumed in moderation, complex carbohydrates from whole grains, vegetables, fruits, and legumes provide energy, fiber, B vitamins, and minerals. When attempting to completely eliminate carbohydrates, the body switches to alternative energy sources, which can be used therapeutically for certain conditions, but is not a universally safe solution for everyone. [11]

In practice, the body seeks balance, not zero. For most healthy adults, a diet with moderate protein, adequate healthy fats, and a predominance of complex carbohydrates yields better long-term weight and health results than extremes. Large meta-analyses show that low-carbohydrate diets may produce slightly more significant weight loss and improvements in a number of indicators in the first few months, but after a year or more, the differences with a uniformly balanced diet usually even out. [12]

Another important point is context. "Low-carb" can mean a diet rich in vegetables, nuts, and fish, or it can mean a menu of bacon and sausages. "Low-fat" can sometimes translate into excess sugar and refined starches. The same goes for protein: the difference between a serving of fish and a selection of processed meats is huge, even if the grams of protein are the same. For health, it's not just the proportions of macronutrients that matter, but also the quality of the food. [13]

Table 2. Main functions of macronutrients

Nutrient	Key Features	In case of shortage	In excess from unhealthy sources
Squirrels	Construction of muscles, enzymes, hormones, immune proteins [14]	Muscle loss, weakness, decreased immunity	Stress on the kidneys in those predisposed, deficiency of other nutrients with an imbalanced diet [15]
Fats	Hormones, cell membranes, fat-soluble vitamins, protection of the nervous system [16]	Hormonal imbalances, dry skin, impaired absorption of vitamins A, D, E, K	Increased risk of cardiovascular disease with excess saturated and trans fats [17]
Carbohydrates	Energy for the brain and muscles, a source of fiber and a number of vitamins [18]	Fatigue, decreased performance, problems with concentration	Excess fast carbohydrates lead to weight gain and worsening glycemic control [19]

What are the dangers of giving up fats?

The idea of completely eliminating fat from the diet seems logical: a gram of fat provides approximately twice as many calories as a gram of protein or carbohydrates. In practice, attempts to "zero out" fat lead to a deficiency in essential polyunsaturated fatty acids, which the body cannot synthesize on its own. These acids are critical for blood vessels, the brain, vision, and immunity. Long-term deficiency affects the condition of the skin, hair, and mucous membranes and increases the risk of chronic inflammatory processes. [20]

Fats are also necessary for the absorption of vitamins A, D, E, and K. With a diet low in fat, the absorption of these vitamins is significantly impaired, even if they are formally sufficient in foods or supplements. In the long term, this can lead to deterioration of vision in twilight, problems with bone tissue, blood clotting, and antioxidant protection. For people already at risk for osteoporosis, cutting out fats is an additional blow to bones. [21]

The hormonal system also depends on lipids. Sex hormones and cortisol are synthesized from cholesterol, and the membranes of all cells contain phospholipids. Excessive fat restriction, especially in women, is associated with menstrual irregularities, decreased libido, and impaired reproductive function. In athletes who combine low-fat diets with high exercise, this can manifest as functional disorders, bone loss, and fatigue. [22]

Furthermore, when cutting out fat, people often compensate for calories with simple carbohydrates, which increases the glycemic load, exacerbates blood sugar fluctuations, and promotes fat gain. Research shows that diets with an excessive emphasis on low-fat foods and refined carbohydrates offer no benefits in terms of cardiovascular disease risk compared to moderate fat intake with good-quality foods. [23]

Finally, completely fat-free foods are less satiating. Fats affect the production of satiety hormones and slow gastric emptying. Diets with almost zero fat content increase the risk of binge eating on sweets and starchy foods, breakdowns, and late-night snacking. As a result, a person eats more calories than planned, and micronutrient status only worsens. [24]

Table 3. The main consequences of giving up fats

Consequence	Mechanism	What is the threat?
Essential fatty acid deficiency	Lack of polyunsaturated fatty acids in the diet [25]	Dry skin, brittle hair, impaired tissue regeneration
Impaired absorption of vitamins A, D, E, K	Lack of fats for the absorption of these vitamins [26]	Problems with bones, vision, and blood clotting
Hormonal imbalances	Lack of cholesterol and lipids for hormone synthesis [27]	Menstrual irregularities, decreased libido, fatigue
Carbohydrate Crashes and Overeating	Low satiety, cravings for sweets [28]	Fat gain, weight fluctuations, worsening glycemia

The dangers of cutting out carbohydrates

Carbohydrates are often touted as the "main enemy of figure," especially simple sugars and white baked goods. Against this backdrop, very low-carb and ketogenic diets have gained popularity. In the short term, such diets often result in significant weight loss and improvements in a number of metabolic indicators, especially in people with type 2 diabetes and metabolic-associated liver disease. [29]

However, completely eliminating carbohydrates or extreme restrictions below approximately 20-30 grams per day are not always justified. Systematic reviews note that most of the benefits of low-carb diets are related to the overall calorie deficit and the avoidance of ultra-processed foods, rather than the zero-carb diet itself. Over time, the weight-loss benefits compared to a moderately carbohydrate-rich balanced diet diminish, and long-term safety concerns remain. [30]

Very low carbohydrate intake can cause fatigue, headaches, decreased physical and mental endurance, and constipation due to a lack of fiber. With long-term adherence, some studies indicate a possible increased risk of cardiovascular disease and overall mortality if carbohydrates are replaced primarily by animal fats and proteins rather than plant sources. [31]

In type 2 diabetes and a comprehensive approach, low-carbohydrate and ketogenic diets can be beneficial for blood sugar control and weight loss, but require medical supervision, adjustments to therapy, and monitoring of lipid profiles, kidney function, and liver function. Guidelines emphasize that this is one possible tool, not a universal standard of care for everyone. [32]

For healthy people without significant metabolic disorders, it makes more sense to limit fast carbohydrates and sources of "empty calories" while preserving complex carbohydrates from whole grains, vegetables, fruits, and legumes. This approach allows for weight control, normal brain and intestinal function, and dietary variety without extremes. [33]

Table 4. Low-carb diets: pros and cons

Aspect	Potential benefits	Potential downsides
Weight control	At the beginning, they can provide a faster reduction in body weight due to water and fat [34]	After a year, the difference with other diets decreases; the overall calorie deficit is more important.
Metabolic health	Improving glycemia and triglycerides in people with type 2 diabetes and metabolic disorders [35]	The long-term effects of severe carbohydrate restriction, especially without medical supervision, are unclear.
Well-being	Some people experience a decrease in appetite and cravings for sweets [36]	Others experience fatigue, headaches, problems with concentration, constipation.
Risks	Replacing carbohydrates with animal fats and proteins may increase the risk of mortality and cardiovascular disease [37]	Extreme regimens require special caution in people with kidney, liver, and heart disease.

Why is protein deficiency dangerous?

Trying to lose weight by cutting primarily fat and protein is a common mistake. Protein provides calories, so people try to reduce it along with everything else. As a result, a person may eat a normal amount of carbohydrates but clearly be under-consuming protein, especially if the diet is vegetarian, poorly planned, or very low in calories. [38]

When protein is deficient, the body begins to use amino acids from muscles and internal organs to support vital functions. Body weight appears to decrease, but a significant portion of the loss is muscle, not fat. This subsequently slows metabolism, reduces strength and endurance, impairs the ability to maintain weight, and dramatically increases the risk of falls and fractures in old age. [39]

Protein is also important for the immune system. Antibodies, many components of the complement system, and acute-phase reactants all require amino acids. Chronic protein deficiency increases susceptibility to infection, delays wound healing, and increases the risk of complications after surgery and serious illnesses. This factor is often underestimated when attempting to lose weight through long-term mono-diets and extremely low-protein diets. [40]

High-protein diets can be beneficial for maintaining muscle mass and controlling appetite, especially in overweight individuals and those following weight loss. However, it's important not to go to extremes. Several reviews note that very high protein intake from red and processed meats, especially with low levels of plant foods, can increase the risk of cardiovascular disease and overload the kidneys in predisposed individuals. [41]

The optimal strategy is considered to be a moderate increase in protein intake to the upper limit of normal values, with an emphasis on high-quality sources: fish, poultry, legumes, dairy products, nuts, and soy. This approach helps preserve muscle, improve satiety, and facilitate weight maintenance without unnecessary risk to the kidneys and heart in healthy individuals. For people with kidney and liver disease, a protein regimen is determined separately by a doctor. [42]

Table 5. What happens with protein deficiency and excess

Situation	What's happening	Main risks
Protein deficiency when losing weight	The body “eats” muscles, strength and metabolism decrease [43]	Slow metabolism, risk of falls and fractures, difficulty maintaining weight
Extremely low-protein diets	Lack of protein for the immune system, enzymes and hormones [44]	Deterioration of immunity, weakness, deterioration of the quality of skin, hair, nails
A very high protein diet based on red meat and processed foods	Excess saturated fat and salt, stress on the kidneys in those predisposed [45]	Increased risk of cardiovascular and kidney disease
Moderately increased protein intake from quality sources	Better muscle preservation, satiety, appetite control [46]	In the absence of kidney disease, it is usually safe and beneficial.

Why Crash Diets Interfere with Healthy Weight Loss

Any diet based on the complete elimination of fats, proteins, or carbohydrates is essentially an extreme intervention in metabolism. Such regimens create a deficit not only of calories but also of many vital substances: vitamins, minerals, essential fatty acids, and amino acids. In the short term, this may not be noticeable, but if continued for months and years, the risk of complications increases. [47]

The psychological consequences are no less significant. Strictly banning entire food groups fosters "black-and-white" thinking, guilt at the slightest deviation, and increases the risk of binge eating. Research on low-calorie diets and unilateral restrictions shows a link with increased depressive symptoms, sleep disturbances, and increased stress levels, especially in obese individuals. [48]

From a physiological perspective, a prolonged, severe calorie and nutrient deficit leads to an adaptive reduction in energy expenditure: the body expends less energy at rest, thermogenesis decreases, and activity declines. This makes further weight loss more difficult and contributes to rapid weight gain after returning to a more calorie-dense diet. The more extreme the diet, the higher the likelihood of a rebound. [49]

Bone tissue is a separate issue. Rapid weight loss, coupled with a deficiency of calcium, vitamin D, protein, and trace elements (magnesium, zinc, and boron), accelerates bone mineral density loss. This is especially true for women over 40, people with low body weight to begin with, and patients following bariatric surgery. Osteoporosis guidelines emphasize that diet during weight loss must take bone health into account. [50]

Over the long term, extreme diets worsen your relationship with food and your body. People switch from one "miracle plan" to another, losing and gaining the same 5-10 kilograms, but gradually losing muscle mass, slowing metabolism, and increasing the risk of chronic diseases. It's far more effective to develop a realistic, balanced strategy once than to live in a constant state of "eating swings." [51]

Table 6. Why extreme diets rarely work in the long run

Factor	Short-term effect	Long-term consequences
Drastic reduction of calories	Rapid weight loss due to water, glycogen and some fat [52]	Slow metabolism, breakdown, rapid weight gain
Eliminating an entire food group	Simple rule, feeling of control [53]	Nutrient deficiencies, problems with bones, skin, hair
Strict prohibitions	Temporary "inspiration" and a quick start [54]	Increased anxiety, depressive symptoms, eating disorders
Poor support	The illusion of a “miracle” due to one scheme [55]	Loss of trust in recommendations, cycles of "diet - failure"

How to Lose Weight Safely

For safe weight loss, it's best not to demonize individual macronutrients, but to instead create a moderate calorie deficit tailored to your individual needs. In practice, this means: sufficient protein to preserve muscle, a reasonable amount of fat with an emphasis on unsaturated, complex carbohydrates over fast ones, and sufficient fiber, vitamins, and minerals. [56]

Protein is generally recommended to be kept at a level of no less than 1.2-1.6 grams per kilogram of body weight during weight loss to maintain muscle tissue, especially during strength training. Fats should ideally comprise at least 20-30% of the total energy intake, with priority given to vegetable oils, nuts, seeds, and fatty fish. The remaining calories are filled primarily by complex carbohydrates. Specific amounts are determined individually, taking into account any medical conditions and doctor's recommendations. [57]

Particular attention should be paid to the quality of carbohydrates. Instead of sugary drinks, white baked goods, and confectionery, it's better to base your diet on whole-grain bread, whole-grain cereals, legumes, vegetables, and fruits. This provides energy, fiber, vitamins, and minerals, improves glycemic control, and helps keep appetite under control. [58]

In addition to nutrition, physical activity is important: a combination of aerobic exercise and strength training. Strength training helps maintain and build muscle mass, while aerobic exercise improves insulin sensitivity and cardiovascular health. Current guidelines for obesity treatment and osteoporosis prevention consider exercise a mandatory part of the program, not an optional extra. [59]

Finally, if you have chronic conditions (diabetes, kidney disease, liver disease, or cardiovascular disease), the choice of diet, especially low-carbohydrate or high-protein diets, should be discussed with a physician or clinical nutritionist. For some patients, such regimens can provide significant benefits, but require medication adjustments and regular monitoring. Self-experimentation with the principle of "cutting out everything containing carbohydrates or fat" is particularly risky in such situations. [60]

Table 7. Approximate principles of safe weight loss

Direction	A practical approach
Protein	About 1.2-1.6 g per kilogram of body weight during weight loss, mainly from fish, poultry, legumes, and dairy products [61]
Fats	At least 20-30% of energy, emphasis on vegetable oils, nuts, seeds, fatty fish, limiting trans fats and excess saturated fats [62]
Carbohydrates	Complex carbohydrates from whole grains, vegetables, fruits and legumes, limiting sugar and refined starch [63]
Calorie deficit	Moderate deficiency, usually around 10-25% of maintenance level, without extreme starvation [64]
Health control	Regular assessment of well-being; in case of chronic diseases – monitoring of tests and consultation with a doctor [65]

Brief FAQ

Is it true that you need to completely eliminate fats to lose weight?
No. Fats are essential for hormonal balance, vitamin absorption, and nervous system function. It's important to reduce excess unhealthy fats and overall calorie intake, but eliminating fats completely is both impossible and harmful. [66]

Is it dangerous to completely eliminate carbohydrates?
Completely eliminating carbohydrates requires medical supervision and is not suitable for everyone. For most people, it is safer to limit fast carbohydrates and maintain complex carbohydrates rich in fiber and micronutrients. [67]

Is it possible to significantly cut protein if you "just need fewer calories"?
No. Protein is needed to maintain muscle, immunity, and normal metabolism. When it's deficient, weight loss comes from muscle rather than fat, metabolism slows, and maintaining the results becomes more difficult. [68]

What is the safest diet for long-term use?
The most sustainable and safe options are considered to be moderately low-calorie, balanced diets that contain sufficient protein, healthy fats, and complex carbohydrates, plenty of vegetables, and minimally processed foods. Specific proportions are tailored to the individual and their condition. [69]

Where should you start if you want to lose weight without harming your health?
It's best to start by analyzing your current diet, reducing ultra-processed foods and sweets, gradually reducing calories, increasing the amount of vegetables, protein, and healthy fats, and adding regular physical activity. Then, if necessary, discuss individual nuances with a doctor or nutritionist. [70]