Thirst and Lack of Appetite: Know What They May Be Signaling

When someone develops a profound loss of appetite or extreme thirst, a serious underlying health concern might explain the symptoms at hand. Learn about three possibilities that could be at work.

​Read more:​ I Drink Enough Water but Still Feel Dehydrated

One thirst-related condition is diabetes insipidus, which occurs when your kidneys are unable to retain water, according to the Pituitary Foundation.

Diabetes insipidus affects roughly one of every 25,000 people, the foundation notes. It's distinct from the much more common form of the disease, diabetes mellitus (Type 1 or Type 2). While the latter is characterized by a dangerous inability of the body to control blood sugar levels, people with diabetes insipidus have no such problem.

However, the inability to retain water is a very serious issue, the foundation notes, and it causes people with diabetes insipidus to urinate far more than normal, day and night. While a healthy adult urinates an average of 1 to 2 quarts a day, a person struggling with a serious bout of diabetes insipidus could urinate as much as 20 quarts daily, according to the Mayo Clinic.

The result, says the Mayo Clinic, is that people typically see their thirst levels skyrocket, no matter how much they drink.

While excessive thirst and drinking are the main symptoms, a certain type of diabetes insipidus, called nephrogenic diabetes insipidus, can also give rise to a lack of appetite, the Pituitary Foundation says. This form, says the Mayo Clinic, occurs when a defect in the kidney's structure renders it unable to properly respond to the anti-diuretic hormone (ADH). ADH is what normally ensures that bodily fluids are excreted at a normal pace.

Both the Pituitary Foundation and the Mayo Clinic indicate that, in addition to a lack of appetite, people may also experience vomiting. Weight loss may also ensue, adds the Mayo Clinic. Appetite loss can ultimately affect anyone with diabetes insipidus because chronic fluid loss can trigger a severe imbalance in key electrolytes, such as sodium and potassium.

Another driver of excessive thirst is diabetic ketoacidosis. According to the Mayo Clinic, it's most commonly a complication of Type 1 diabetes, though in rare instances it may also affect people with Type 2 diabetes.

The Mayo Clinic explains that diabetic ketoacidosis takes hold when blood acid (ketone) levels rise too high. That can happen when levels of insulin — critical to maintaining a good blood sugar balance — plummet. That can occur when either an illness or infection drives up levels of hormones such as adrenaline and cortisol, both of which can interfere with insulin. It can also transpire if diabetes is poorly managed.

When diabetic ketoacidosis develops, the main symptoms are extreme thirst, frequent urination, nausea and vomiting, abdominal pain, weakness and fatigue, notes the Mayo Clinic.

For people concerned about a striking loss of appetite, the National Institute of Mental Health (NIMH) points to a potentially life-threatening disorder driven by a distorted body image, an intense fear of gaining weight and an inclination toward extreme food restriction: anorexia nervosa.

The NIMH explains that people with the disorder often weigh themselves repeatedly, exercise far more than normal and express little to no interest in food. And those who do eat sometimes force themselves to vomit right afterward or take laxatives to lose weight, even if they have severe underweight.

"The word anorexia, used alone in the medical world, refers to loss of appetite or lack of desire to eat," notes Lona Sandon, PhD, RDN, an associate professor in the Department of Clinical Nutrition at the School of Health Professions at UTSouthwestern Medical Center, Dallas. "Physiological hunger may exist, but the hedonic interest in food may just not be there."

As a clinical term, "'anorexia nervosa' refers specifically to the eating disorder in which there is an intention not to eat," Sandon explains. Typically, it's often accompanied, she says, by stress, anxiety and other serious psychological disorders, such as depression.

The NIMH further warns that, if left untreated, anorexia can lead to bone thinning, serious heart trouble, organ failure and even starvation. The condition contributes to more fatalities than any other mental disorder, the institute notes.

​Read more:​ 7 Signs Your 'Healthy Diet' Is Actually Disordered Eating

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