Malnutrition

Types of malnutrition

Undernutrition

• Disease-related malnutrition: the most common type in the US, caused by illness that reduces appetite or absorption, or increases needs.
• Starvation-related: from not having enough food, or from eating disorders.
• Wasting: low weight for height, often after acute illness or food shortage.
• Stunting: low height for age in children from long-term undernutrition.

In children, severe forms include marasmus (severe wasting) and kwashiorkor (swelling from protein deficiency).

Micronutrient deficiencies

Lack of specific vitamins and minerals, such as iron, vitamin B12, vitamin D, folate, zinc and vitamin C. These can occur even in people who are normal weight or overweight.

Overnutrition

Excess energy intake leading to overweight and obesity. People with obesity can also be undernourished in protein or micronutrients.

Signs and symptoms

• unintended weight loss, loose clothes, belts, rings or dentures
• reduced appetite and interest in food and drink
• tiredness, low energy and weakness
• muscle wasting, especially in the arms, legs and temples
• feeling cold
• poor concentration, low mood and irritability
• frequent or prolonged infections
• slow wound healing and pressure sores
• dry skin, brittle nails and thinning hair
• swelling of the legs or belly in severe protein deficiency
• in children: poor growth, slow weight gain, irritability or lethargy

Specific deficiency clues

Causes and risk factors

• reduced intake: poor appetite from illness, depression, dementia, chewing or swallowing problems (dysphagia), mouth pain, nausea, social isolation, poverty and food insecurity
• poor absorption: celiac disease, Crohn's disease, chronic pancreatitis, short bowel syndrome, bariatric surgery
• increased needs: cancer, infections, major surgery, burns, chronic lung or heart disease
• eating disorders, including anorexia nervosa
• alcohol use disorder
• medicines that reduce appetite or cause nausea
• older age: reduced appetite, taste and smell, dental problems, mobility limitations and living alone

Screening and diagnosis

Hospitals, nursing homes and many clinics screen for malnutrition using tools such as the Malnutrition Universal Screening Tool (MUST) or the Mini Nutritional Assessment for older adults. Diagnosis often follows GLIM criteria, which combine:

• unintended weight loss, low BMI or reduced muscle mass, and
• reduced food intake or absorption, or illness-related inflammation

Other assessments include:

• a diet history and food diary
• weight and height, BMI, and mid-upper arm circumference
• grip strength
• blood tests for anemia, vitamins, minerals, kidney and liver function (albumin alone is not a reliable marker of nutrition)

Treatment

Nutrition support

• food first: small, frequent, energy- and protein-rich meals and snacks, fortifying foods with milk powder, cheese, butter or oil
• oral nutritional supplements: high-calorie, high-protein drinks
• vitamin and mineral supplements for specific deficiencies
• tube feeding (enteral nutrition) when eating by mouth is not enough or unsafe
• IV nutrition (parenteral) when the gut cannot be used

A registered dietitian tailors the plan.

Treating the cause

• managing nausea, pain, depression and dental problems
• speech and swallowing therapy for dysphagia
• treating gut diseases
• support for eating disorders and alcohol use
• social support: meal delivery services, help with shopping and cooking, food assistance programs

Refeeding syndrome

In people who have eaten very little for several days or longer, restarting nutrition too quickly can cause dangerous shifts in phosphate, potassium and magnesium, leading to heart and breathing problems. Refeeding syndrome is prevented by starting slowly, giving thiamine and monitoring blood levels.

Complications

• weakened immunity and more infections
• muscle loss, falls and fractures, especially in older adults
• slow healing and pressure ulcers
• longer hospital stays and higher risk of death after illness or surgery
• in children: stunted growth and developmental delays

Prevention

• regular weighing for older adults and people with chronic illness
• noticing and acting early on appetite loss
• eating a varied diet with protein at each meal
• staying active to maintain muscle
• checking on older neighbors and relatives who live alone

Frequently asked questions

What are the first signs of malnutrition?

Early signs include unintended weight loss, loose clothes or rings, reduced appetite, tiredness, feeling cold, poor concentration and getting ill more often. In children, slow weight gain or growth is often the first sign.

What causes malnutrition in the elderly?

Common causes are reduced appetite, chewing or swallowing problems, dementia, depression, living alone, limited mobility, medicines that affect appetite, and chronic illnesses. Poverty and difficulty shopping or cooking also contribute.

Can you be overweight and malnourished?

Yes. A person can take in plenty of calories but too little protein, vitamins or minerals, or lose muscle during illness while remaining overweight. Malnutrition is about nutrient balance and body composition, not just weight.

How is malnutrition treated?

Treatment involves increasing energy and protein intake with fortified foods and supplement drinks, correcting vitamin and mineral deficiencies, and treating the underlying cause. Severe cases may need tube or IV feeding, with careful monitoring to avoid refeeding syndrome.