What are the diseases caused by macronutrient deficiency?

November 1, 2025 •

4 min read

Over 925 million people worldwide suffer from chronic undernutrition, a condition often rooted in macronutrient deficiencies. When the body doesn't receive enough of the essential macronutrients—proteins, fats, and carbohydrates—it cannot function properly, leading to a spectrum of debilitating and potentially fatal diseases. This includes conditions like protein-energy malnutrition, which encompasses kwashiorkor and marasmus.

Quick Summary

Macronutrient deficiency can cause severe conditions like kwashiorkor, marasmus, and essential fatty acid deficiency. Symptoms range from extreme wasting and stunted growth to edema, skin issues, and neurological problems, highlighting the need for a balanced diet.

Key Points

Protein-Energy Malnutrition: Severe deficiency can lead to Kwashiorkor (characterized by edema) and Marasmus (extreme muscle and fat wasting).
Essential Fatty Acid Deficiency: A lack of healthy fats can cause scaly dermatitis, hair loss, impaired immunity, and neurological problems.
Carbohydrate Deficiency: While not essential, very low carb intake can lead to ketosis and, in rare severe cases like in uncontrolled diabetes, ketoacidosis.
Common Symptoms: Signs of macronutrient deficiency include stunted growth, low body weight, fatigue, weakened immune response, and skin issues.
Diagnosis and Prevention: These conditions are diagnosed through physical examination and lab tests, and are best prevented with a balanced, varied diet.

The Foundation of Health: Understanding Macronutrient Needs

Macronutrients—proteins, carbohydrates, and fats—are the primary energy sources and building blocks for the human body. A balanced intake is crucial for growth, metabolism, immune function, and overall health. A deficiency in one or more of these essential nutrients can lead to malnutrition, causing serious health issues. In developing nations, insufficient intake is common, while in developed countries, poor food choices, restrictive diets, or medical conditions like malabsorption are often the cause.

Protein Deficiency: Kwashiorkor and Marasmus

Protein-energy malnutrition (PEM) is a life-threatening condition resulting from insufficient protein and/or calorie intake. The two most severe forms, primarily affecting children, are kwashiorkor and marasmus, both with distinct clinical presentations.

Kwashiorkor

Derived from an African term meaning "the sickness the baby gets when the new baby comes," kwashiorkor typically affects older infants and toddlers who are weaned from breastfeeding to a diet high in carbohydrates but critically low in protein. The distinguishing feature is edema, or fluid retention, which causes a swollen, distended abdomen and puffy extremities. Other symptoms include changes in skin pigment, flaky dermatitis, and hair that becomes thin, dry, and discolored. The presence of edema can deceptively mask the underlying severe muscle wasting. This condition also severely impairs the immune system, making children highly susceptible to infection.

Marasmus

Marasmus results from a severe deficiency of all macronutrients—protein, carbohydrates, and fats. It leads to a state of emaciation and visible wasting of muscle and fat tissue. Unlike kwashiorkor, edema is not present, giving the child a shriveled, withered appearance with loose, wrinkled skin hanging in folds. Other symptoms include stunted growth, dry skin, brittle hair, and reduced body temperature, heart rate, and blood pressure. Children with marasmus are often lethargic, weak, and apathetic due to a complete lack of energy.

Fat Deficiency and Its Broad Impact

Fat is a crucial macronutrient, not only as an energy source but also for absorbing fat-soluble vitamins (A, D, E, K) and producing hormones. A deficiency, particularly of essential fatty acids (EFAs) like omega-3 and omega-6, can have widespread health consequences.

Essential Fatty Acid Deficiency (EFAD)

Dermatitis: A key symptom is a dry, scaly rash that can cover the skin.
Growth Issues: In infants and children, EFAD can cause stunted growth and failure to thrive.
Hair Loss: The hair may become dry and brittle, leading to significant hair loss.
Impaired Immune Response: Fats are vital for immune cell function. A deficiency can weaken the immune system, increasing susceptibility to infections and impairing wound healing.
Neurological Problems: As EFAs are crucial for brain function, deficiency can lead to cognitive decline and neurological issues.
Hormonal Imbalances: Since fats are involved in hormone production, a lack can disrupt hormonal balance, potentially causing reproductive issues.

The Effects of Carbohydrate Deficiency

Unlike protein and fat, carbohydrates are not strictly considered essential as the body can produce glucose from other macronutrients through gluconeogenesis. However, insufficient carbohydrate intake can have significant side effects.

Ketosis and Potential Acidosis

When carbohydrate intake is severely restricted, the body uses stored fat for energy, producing ketone bodies. This metabolic state is known as ketosis. While often harmless, a prolonged or uncontrolled overproduction of ketones, especially in individuals with diabetes, can lead to ketoacidosis. This is a life-threatening condition where the blood becomes dangerously acidic. Symptoms of ketosis can include headaches, fatigue, and bad breath, while ketoacidosis is a medical emergency with more severe signs like extreme thirst and confusion. For the general population, low carb intake can also lead to fatigue, reduced athletic performance, and constipation due to lack of fiber.

Diagnosing and Treating Macronutrient Deficiencies

Diagnosis typically involves a comprehensive evaluation of a person's diet, medical history, and physical symptoms. A doctor may take measurements of height and weight or mid-upper arm circumference to assess wasting, especially in children. Blood tests can identify specific micronutrient deficiencies that often accompany macronutrient deficiencies, such as low iron, zinc, or vitamins A, D, E, and K, which are dependent on fat absorption.

Treatment varies depending on the severity of the condition. In cases of severe malnutrition like marasmus or kwashiorkor, treatment involves a cautious refeeding process under medical supervision to avoid refeeding syndrome, a potentially fatal shift in fluid and electrolytes. For less severe deficiencies, a balanced diet rich in all macronutrients is recommended. Specific nutritional supplements may also be used.

Comparing Kwashiorkor and Marasmus


Feature	Kwashiorkor	Marasmus
Primary Cause	Severe protein deficiency with relatively adequate calorie intake.	Deficiency of all macronutrients (protein, carbohydrates, and fats).
Key Symptom	Edema (swelling), particularly in the abdomen and limbs.	Extreme muscle and fat wasting, leading to emaciation.
Appearance	Bloated or pot-bellied, but limbs appear thin.	Severely underweight with visible bones and loose, wrinkled skin.
Skin	Dry, flaky, and prone to lesions and pigment changes.	Dry, thin, and inelastic.
Hair	Thin, sparse, discolored, and easily pulled out.	Dry and brittle.
Growth	Stunted growth is common.	Severe growth retardation.
Behavior	Apathetic and irritable.	Lethargic, weak, and apathetic.

Conclusion: The Importance of a Balanced Diet

Macronutrient deficiencies can result in a range of serious health problems, from severe wasting and edema to dermatological issues and metabolic complications. The most effective strategy for preventing these conditions is consuming a healthy, balanced diet with adequate intake of protein, healthy fats, and complex carbohydrates. For those at risk due to specific health conditions or restrictive eating, regular monitoring and consultation with a healthcare professional or registered dietitian is vital. Prioritizing proper nutrition is a crucial step towards long-term health and disease prevention. For more in-depth medical information on protein-energy malnutrition, refer to the Protein-Energy Malnutrition article on the MSD Manuals website.

Frequently Asked Questions

Kwashiorkor is primarily caused by a severe protein deficiency despite adequate calorie intake, resulting in edema and a swollen belly. Marasmus, conversely, is a deficiency of all macronutrients, leading to extreme wasting of fat and muscle tissue.

Signs of fat deficiency, particularly essential fatty acid deficiency (EFAD), include a dry, scaly rash (dermatitis), hair loss, slower wound healing, and a weakened immune system.

Without sufficient carbohydrates, the body burns fat for energy, producing ketones in a process called ketosis. While this is often harmless, it can cause fatigue, headaches, and in diabetics, potentially dangerous ketoacidosis.

Macronutrient deficiencies are typically diagnosed through a physical examination, assessment of symptoms like wasting or edema, and measurement of height and weight. Lab tests, including blood work for protein and micronutrient levels, can also be used.

Yes, refeeding syndrome is a potentially life-threatening complication that can occur when severely malnourished individuals begin refeeding. It is a rapid shift in fluids and electrolytes, requiring close medical supervision, especially in the initial stages of treatment.

Long-term effects of severe malnutrition can include permanent physical and mental disabilities, stunted growth, and a higher predisposition to certain chronic diseases.

The best way to prevent macronutrient deficiency is to consume a healthy, balanced diet that includes a variety of protein sources (lean meat, fish, eggs, beans), healthy fats (nuts, seeds, olive oil), and complex carbohydrates (whole grains, vegetables, fruits).