Eating a Balanced Diet: Overnutrition vs. Undernutrition

Nutrition is one of the most important influences on health, which is why eating a balanced diet is so crucial. It is the balance of nutrients contained in the calories you consume, weighed against the calories you burn, that impacts overall wellness. Nutritional imbalances such as overnutrition and undernutrition may lead to malnutrition and severe health difficulties. Read on to learn more.

Overnutrition is frequent or habitual overconsumption of nutrients by eating too much food, to the point that it becomes dangerous to your health. Overnutrition, also known as obesity, is a form of malnutrition. "The World Health Organization has recently added overnutrition to its definition of malnutrition to recognize the detrimental health effects that can be caused by excessive consumption of nutrients," states the Cleveland Clinic. "This includes the effects of overweight and obesity, which are strongly associated with a list of noncommunicable diseases. It also includes the toxicity that can result from overdosing specific micronutrients."

Translation: Even when you are eating too much, you can still develop a deficiency in certain nutrients if you fail to consume the proper variety of foods. In this way, you can be both overnourished and malnourished.

Nutrients are compounds necessary for bodily function; they include minerals, vitamins, fats, carbohydrates and proteins. Although most nutrients can be harmful in excess, the danger of overnutrition relates strongly to carbohydrates and fats, according to a September 2021 article by the ‌American Society for Nutrition.‌

"[Researchers] lay much of the blame for the current obesity epidemic on excessive consumption of foods with a high glycemic load: in particular, processed, rapidly digestible carbohydrates," they write. "These foods cause hormonal responses that fundamentally change our metabolism, driving fat storage, weight gain, and obesity. When we eat highly processed carbohydrates, the body increases insulin secretion and suppresses glucagon secretion. This, in turn, signals fat cells to store more calories, leaving fewer calories available to fuel muscles and other metabolically active tissues."

Overeating (aka binge eating) differs conceptually from overnutrition, although they are essentially the same thing in action. Whereas overeating is a compulsion considered a psychological disorder, overnutrition is volitionally choosing to eat more food than you need, even if you don't realize it. Over time, the effects can have a serious negative impact on your body systems. Overnutrition increases total body fat and places excess fat around the internal organs, per the Cleveland Clinic.

The metabolic effects of overnutrition include heart disease, diabetes, stroke, high blood pressure and certain cancers, notes the World Health Organization (WHO).

Undernutrition is another type of malnutrition. According to September 2022 research in ‌Merck Manuals‌, it can be a result of "inadequate ingestion of nutrients, malabsorption, impaired metabolism, loss of nutrients due to diarrhea, or increased nutritional requirements (as occurs in cancer or infection)."

Undernutrition happens gradually. According to the ‌Merck Manuals‌ research, nutrient levels in blood and tissues change first, followed by intracellular changes in biochemical functions and structure. And ultimately, symptoms and signs appear.

"When the body is deprived of nourishment for an extended period of time, it goes into 'survival mode," per Oregon State University. "The first priority for survival is to provide enough glucose or fuel for the brain. The second priority is the conservation of amino acids for proteins... As starvation continues ... proteins from muscles are released and broken down for glucose synthesis."

Undernutrition is associated with poverty and social deprivation, as detailed by WHO. It is also associated with infants, children, adolescents and people who are pregnant. Each of these groups requires an increased demand for nutrients to support the high metabolic state of their particular stage of life or health condition.

Older adults are also at risk of undernutrition due to changes in their metabolism, inability to cook or feed themselves and changes in appetite. Malnutrition and frailty are related syndromes, according to an April 2019 review in ‌Nutrients‌. The review also states taht malnutrition is strongly associated with sarcopenia (loss of muscle strength, function and mass with increasing age), which leads to reduced physical function and dependency.

Abnormal loss of lean body mass, such as that found in malnutrition, is responsible for the many complications of undernutrition, such as an increase in susceptibility to infections.

Cachexia is a weight loss greater than 5 percent of body weight in 12 months or less in the presence of chronic illness, per the Society on Sarcopenia, Cachexia & Wasting Disorders.

And according to the previously mentioned ‌Merck Manuals‌ article, cachexia is evidenced by shrinking muscle mass and protruding bones. The skin becomes dry and inelastic, and the hair falls out. The risk of pressure ulcers and hip fractures increases with cachexia.

"[Undernutrition] may develop slowly when it is due to anorexia, or very rapidly, as sometimes occurs when it is due to rapidly progressive cancer-related cachexia," the article states.

Malnutrition is the condition that occurs when your body does not get enough nutrients, per the National Institutes of Health (NIH). You may develop malnutrition if you lack a single vitamin in your diet. Lacking a vitamin or other nutrient is called a deficiency.

Malnutrition it is not synonymous with undereating because, as previously explained, it can occur despite overeating. This is because your body requires a balance of many different nutrients. Proper nutrition means eating a balanced diet of all nutrients, and they are not present in every food.

Causes of malnutrition unrelated to the amount of food you eat include digestion and nutrient-absorption problems, per the NIH.

The importance of eating a balanced diet cannot be overstated. Unfortunately, malnutrition is rampant all over the world.

According to the Government of Canada (GC), the prevalence of malnutrition worldwide is staggering. Globally, over 2.3 billion people suffer from malnutrition in one form or another. Of these, 29.9 percent of people assigned female at birth (AFAB) aged 15 to 49 years are affected by anemia, [and] 40 percent of all people assigned male at birth (AMAB) and AFAB have overweight or obesity.

It's often thought that malnutrition is uncommon in developed countries. But the truth is, even people in developed countries are at risk for nutritional deficiencies. Poverty, natural disasters, political problems and war can all contribute to malnutrition and starvation, and not just in developing countries, the NIH notes.

People AFAB are at higher risk of being affected by malnutrition, per the GC. Sixty percent of the world's hungry are people AFAB. People AFAB are also at heightened risk of malnutrition due to systematic discrimination; people AFAB typically eat the least and eat last, per the GC.

All of that said, common nutritional deficiencies do differ by country. For example, thiamin — vitamin B1 — deficiencies "are widely reported where polished rice and milled cereals are the primary food source," per a July 2022 review in ‌StatPearls‌.

There are many micronutrients with a high likelihood for deficiency in the U.S. Specifically, 94.3 percent of the U.S. population do not meet the daily requirement for vitamin D, per the Linus Pauling Institute at Oregon State University.

Other common deficiencies in the U.S. population include 88.5 percent for vitamin E, 52.2 percent for magnesium, 44.1 percent for calcium, 43 percent for vitamin A and 38.9 percent for vitamin C, per the Linus Pauling Institute at Oregon State University.

For the nutrients in which a requirement has not been set, 100 percent of the population had intakes lower than the AI for potassium, 91.7 percent for choline and 66.9 percent for vitamin K.

Malnutrition happens in stages: First, blood and tissue changes occur, then metabolic processes go awry and finally, signs and symptoms occur. One of these is compromised immunity, says the Harvard T.H. Chan's School of Public Health.

Malnutrition or a diet lacking in one or more nutrients can impair the production and activity of immune cells and antibodies, per the Harvard T.H. Chan School of Public Health.

One of the effects of malnutrition is poor wound healing. When the body does not get enough protein, carbohydrates and vitamins, it cannot heal.

One of the first systems to begin to shut down is the immune system, per the Cleveland Clinic. This makes undernourished people highly prone to illness and infection and slower to recover. Wounds take longer to heal.

Overnutrition, or obesity, is also associated with poor wound healing. Obesity increases the risk of infection after surgery, per Mount Sinai. Having overweight can also put tension on stitches, which can make them break open.

According to the ACUTE Center for Eating Disorders at Denver Health, severe malnutrition can result in a multitude of serious illnesses, including anemia, aspiration pneumonia, hypoglycemia, bone loss, brain atrophy, liver disease, bowel disorders, myocardial atrophy and mitral valve prolapse.

Left untreated, malnutrition can lead to mental or physical disability, illness and possibly death, warns the NIH.