The World Health Organization (WHO) recommends rehydrating a severely undernourished child who has diarrhea relatively slowly. The preferred method is with fluids by mouth using a drink called oral rehydration solution (ORS). The oral rehydration solution is both slightly sweet and slightly salty and the one recommended in those with severe undernutrition should have half the usual sodium and greater potassium. Fluids by nasogastric tube may be use in those who do not drink. Intravenous fluids are recommended only in those who have significant dehydration due to their potential complications. These complications include congestive heart failure. Over time, ORS developed into ORT, or oral rehydration therapy, which focused on increasing fluids by supplying salts, carbohydrates, and water. This switch from type of fluid to amount of fluid was crucial in order to prevent dehydration from diarrhea.

Breast feeding and eating should resume as soon as possible. Drinks such as soft drinks, fruit juices, or sweetened teas are not recommended as they contain too much sugar and may worsen diarrhea. Broad spectrum antibiotics are recommended in all severely undernourished children with diarrhea requiring admission to hospital.

To prevent dehydration readily available fluids, preferably with a modest amount of sugars and salt such as vegetable broth or salted rice water, may be used. The drinking of additional clean water is also recommended. Once dehydration develops oral rehydration solutions are preferred. As much of these drinks as the person wants can be given, unless there are signs of swelling. If vomiting occurs, fluids can be paused for 5–10 minutes and then restarting more slowly. Vomiting rarely prevents rehydration as fluid are still absorbed and the vomiting rarely last long. A severely malnourished child with what appears to be dehydration but who has not had diarrhea should be treated as if they have an infection.

For babies a dropper or syringe without the needle can be used to put small amounts of fluid into the mouth; for children under 2, a teaspoon every one to two minutes; and for older children and adults, frequent sips directly from a cup. After the first two hours, rehydration should be continued at the same or slower rate, determined by how much fluid the child wants and any ongoing diarrheal loses. After the first two hours of rehydration it is recommended that to alternate between rehydration and food.

In 2003, WHO and UNICEF recommended a reduced-osmolarity ORS which still treats dehydration but also reduced stool volume and vomiting. Reduced-osmolarity ORS is the current standard ORS with reasonably wide availability. For general use, one packet of ORS (glucose sugar, salt, potassium chloride, and trisodium citrate) is added to one liter of water; however, for malnourished children it is recommended that one packet of ORS be added to two liters of water along with an extra 50 grams of sucrose sugar and some stock potassium solution.

Malnourished children have an excess of body sodium. Recommendations for home remedies agree with one liter of water (34 oz.) and 6 teaspoons sugar and disagree regarding whether it is then one teaspoon of salt added or only 1/2, with perhaps most sources recommending 1/2 teaspoon of added salt to one liter water.

Treating malnutrition, mostly through fortifying foods with micronutrients (vitamins and minerals), improves lives at a lower cost and shorter time than other forms of aid, according to the World Bank. The Copenhagen Consensus, which look at a variety of development proposals, ranked micronutrient supplements as number one.

In those with diarrhea, once an initial four-hour rehydration period is completed, zinc supplementation is recommended. Daily zinc increases the chances of reducing the severity and duration of the diarrhea, and continuing with daily zinc for ten to fourteen days makes diarrhea less likely recur in the next two to three months.

In addition, malnourished children need both potassium and magnesium. This can be obtained by following the above recommendations for the dehydrated child to continue eating within two to three hours of starting rehydration, and including foods rich in potassium as above. Low blood potassium is worsened when base (as in Ringer's/Hartmann's) is given to treat acidosis without simultaneously providing potassium. As above, available home products such as salted and unsalted cereal water, salted and unsalted vegetable broth can be given early during the course of a child's diarrhea along with continued eating. Vitamin A, potassium, magnesium, and zinc should be added with other vitamins and minerals if available.

For a malnourished child with diarrhea from any cause, this should include foods rich in potassium such as bananas, green coconut water, and unsweetened fresh fruit juice.

In order to avoid problems, the person must be rehabilitated with small but frequent rations, given every two to four hours. During one week, the diet, hyperglucidic, is gradually enriched in protein as well as essential elements: sweet milk with mineral salts and vitamins. The diet may include lactases - so that children who have developed lactose intolerance can ingest dairy products - and antibiotics - to compensate for immunodeficiency. After two to three weeks, the milk is replaced by boiled cereals fortified with minerals and vitamins until its mass is at least 80% of normal weight. Traditional food can then be reintroduced. The child is considered healed when his mass reaches 85% of normal.

Starving patients can be treated, but this must be done cautiously to avoid refeeding syndrome. Rest and warmth must be provided and maintained. Small sips of water mixed with glucose should be given in regular intervals. Fruit juices can also be given. Later, food can be given gradually in small quantities. The quantity of food can be increased over time. Proteins may be administered intravenously to raise the level of serum proteins.

For the individual, prevention consists of ensuring they eat plenty of food, varied enough to provide a nutritionally complete diet.

Starvation can be caused by factors, other than illness, outside of the control of the individual. The Rome Declaration on World Food Security outlines several policies aimed at increasing food security and, consequently, preventing starvation. These include:

- Poverty reduction

- Prevention of wars and political instability

- Food aid

- Agricultural sustainability

- Reduction of economic inequality

Supporting farmers in areas of food insecurity through such measures as free or subsidized fertilizers and seeds increases food harvest and reduces food prices.

Disorders usually resolve after early treatment. If the treatment is delayed, the overall health of the child is improved but physical (reduced) and intellectual (mental disabilities) sequelae are feared. Without treatment or if treatment occurs too late, death is inevitable.

A high risk of death is identified by a brachial perimeter < 11 cm or by a weight-to-height threshold < -3 SD. In practice, malnourished children with edema are suffering from potentially life-threatening severe malnutrition.

Until the late 20th century, dietary issues in Mexico were solely a question of undernutrition or malnutrition, generally because of poverty and distribution issues. For this reason, obesity was associated with wealth and health, the latter especially in children. Despite changes in the Mexican diet and food distribution, malnutrition still remains problematic in various parts of the country.

Obesity in Mexico is a relatively recent phenomenon, having been widespread since the 1980s with the introduction of processed food into much of the Mexican food market. Prior to that, dietary issues were limited to under and malnutrition, which is still a problem in various parts of the country. Following trends already ongoing in other parts of the world, Mexicans have been foregoing traditional whole grains and vegetables in favor of a diet with more animal products, more fat, and more sugar much of which is a consequence of processed food. It has seen dietary energy intake and rates of overweight and obese people rise with seven out of ten at least overweight and a third clinically obese.