Malnourishment: Nursing pathophysiology

Malnourishment, also called malnutrition, is when there’s an imbalance of nutrients needed to support essential body functions. This imbalance can occur with overnutrition, where nutrient intake is more than the body requires, like with obesity; or with undernutrition, where nutrient intake is insufficient to meet the body’s needs, as seen in starvation.

So, the three primary nutrients crucial for overall health are carbohydrates, proteins, and fats. First, carbohydrates are the primary source of glucose used for energy and include monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides are simple carbohydrates, like table sugar. They are easily broken down and less nutrient-dense. Oligosaccharides and polysaccharides are more complex carbohydrates, like soybeans and whole grains. These take longer to break down and are more nutrient-dense.

Next, proteins are complex chains of amino acids and are the building blocks of the body. They construct tissues and important molecules, like enzymes and hormones, and they repair tissues. Proteins can also be used for energy, if needed. Amino acids are categorized as essential, meaning they must be ingested through the diet, and non-essential, because they are produced within the body. High protein foods include animal products, like meat and dairy, or plant-based foods like legumes and nuts.

Lastly, fats, or lipids, are composed of glycerol and fatty acids. Fats are another source of energy, and they’re a critical component of cells and tissues. They also help absorb fat soluble vitamins and make up important molecules like steroids. Based on their chemical structure, fats are either saturated, like butter, or unsaturated, like the fats found in avocado.

Once ingested, nutrients are broken down by the digestive system, absorbed, and used in various ways. Carbohydrates are broken down into glucose, which is transported throughout the body and used by cells for energy. Any excess glucose is primarily stored as glycogen in the liver and muscles for later use; but once glycogen storage has reached capacity, the remaining glucose is converted into fatty acids and stored as adipose tissue.

Likewise, after proteins are broken down into amino acids, they can be converted into adipose tissue if they're not used by the tissues or for energy.

Lastly, fats are broken down into glycerol and fatty acids and used to make new types of lipids for use by the body, as an energy source, or stored as adipose tissue.

Now, obesity occurs when caloric intake exceeds body requirements and stems from a combination of factors. Lifestyle factors are related to dietary choices, like eating an excess of high-calorie foods or consuming large portions; and activity level, like being physically inactive, or sedentary. Certain endocrine and metabolic conditions can contribute to obesity, like Cushing syndrome, which elevates glucose levels, and hypothyroidism, which slows metabolism. Environmental factors can increase the risk of obesity as well, including low socioeconomic status, since high-calorie, low-nutrient foods tend to be more affordable and accessible; and there’s often less availability of parks and playgrounds. There are also psychosocial factors, like eating in times of stress or depression. Other factors include alterations in the gut microbiome and genetic and epigenetic influences.

On the other hand, starvation can occur when nutritional requirements aren’t met. Sometimes calories are purposely restricted, such as with anorexia nervosa; while in other cases, socioeconomic and environmental factors, like poverty and famine are also involved.