The World Health Organization defines malnutrition as "deficiencies, excesses or imbalances in a person's intake of energy and/or nutrients." The WHO says that there are actually two kinds of malnutrition: "undernutrition" (which includes marasmus and kwashiorkor) and obesity.

 

Two different types of undernutrition are called marasmus and kwashiorkor. Most of the time, people focus on undernourished children, but adults can also be malnourished, especially women.

 

Marasmus is a kind of severe malnutrition that happens when someone gets very little protein or carbohydrates in their diet. Children who have marasmus have a much lower weight than normal and are very thin. One of the ways that nutritionists evaluate whether children have marasmus is by using a special tape measure around . their upper arm. The measure is called "mid-upper arm circumference." A child who is too thin from malnutrition will have a circumference that measures in the red zone of the this special tape measure. Some symptoms of marasmus are being very thin, having dry skin and brittle hair and respiratory infections.

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Kwashiorkor is another kind of undernutrition which happens when someone doesn't get enough protein in their diet. It is more common, especially among children between nine months and two years old. One big reason for this is that they stop breastfeeding and then have to eat other kinds of food, but that food doesn't have sufficient protein for them to grow properly. Children who have kwashiorkor may look thin in some parts of their body except their ankles, feet and belly or they may even look normal but are very small for their ages. This is called stunting. They can also feel fatigued, tired and have a damaged immune system. Nutritionists measure children who are stunted by calculating what is called a z-score, which compares the height of the child and the child's age. That is then compared to a range of normal heights for children at certain ages. 

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Obesity is another type of malnutrition. It happens when someones takes in more energy than they use up. This creates a build up of fat. People who are obese have a higher risk of heart diseases, stroke and diabetes. Heart disease happens when fat deposits build up in people's arteries, so that not enough blood can reach the heart, which does not receive enough oxygen to work properly. Obese people can also have a lot of pain in their joints, like their knees, because they are carrying a lot of weight.

Obesity can be measured with the Body Mass Index or BMI. BMI measures someone's weight in kilograms divided by that person's height in meters. Someone who is overweight has a BMI of more than 25, and someone who is obese has a BMI of 30 or more. A few symptoms of obesity are shortness of breath, pain in the back and in joints and feeling very tired everyday.

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These diseases of malnutrition can occur in places where there is much poverty, and where people either can't afford or can't get access to nutritious foods. Obesity occurs when people consume foods containing high levels of fat, salt or sugar and do not exercise. But obesity can also be a disease of poverty. People who live in "food deserts" may not have stores around that sell fresh food. They might only be able to buy processed foods, with a lot of salt, sugar and fat. This diet can make people obese.

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Malnutrition is treated with re-nutrition programs that help kids get more and better nutrition. Some groups like Action Contre la Faim work with malnourished children to help them get better. Severely malnourished kids need their hydro-electrolyte balance to be re-established and to start to get more energy and protein in their diets. Because malnourished kids are often not interested in eating, some may be able eat certain foods or PlumpyNut, a nutritious food paste. Some malnourished children need nutrition given to them directly in their stomachs. And some of the most malnourished children need nutrients given to them intravenously, This can take a long time.

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Scientists believe that stunted, malnourished children have an unbalanced mix of bacteria in their gut. Certain types of bacteria are in the gut in smaller amounts and others are there in greater amounts. This imbalance is called Pediatric Environmental Enteropathy. This condition may be one of the reasons that re-nutrition does not always work. The child may get food and supplements like PlumpyNut (a nutritious food paste that is given to malnourished kids to help them grow better0 that should help, but the bacteria in their guts are so imbalanced that they continue to have diarrhea and they don't get better. Some scientists think that undernutrition needs to be treated by not only giving a child more nutritious food, but also certain kinds of probiotics that will balance the gastrointestinal ecology so that they can digest food more effectively.

 

To treat obesity, the person can create a healthy eating plan with fewer calories and include some physical activities. Some people use weight management programs that help them keep to a low calorie diet. There are certain medicines to help people to feel less hungry or to not absorb fats from the foods they eat. There are also weight loss devices for example a gastric balloon, which is put in your stomach through your mouth, the doctor then fills it up with salt water. It takes up more room in your stomach so that you eat less. Finally bariatric surgery is for the more severe cases of obesity or for people with type 2 diabetes. There are several kinds of surgeries that help people lose weight by making changes to their digestive system.

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(The sources for this discussion are (textbook) and World Health Organization, "What is malnutrition?' www.who.int/features/qa/malnutrition/en; www.ecole-de-la-denutrition.com