What BMI is likely to result in hospitalization? (+3 facts)

In this article, we will discuss body mass index (BMI) that may require hospitalization due to complications associated with obesity and low weight.

What BMI is likely to result in hospitalization?

You may need hospitalization if you have a BMI <13 kg/m² (underweight), BMI >30 to 34.9 kg/m² (obese), and BMI ≥35 kg/m² (severely obese). However, even if you have a normal BMI, you may need hospitalization in case of an accident, injury, infection, or other underlying disease.

BMI <13 kg/m² (underweight)

If the patient is underweight, he may experience hypoglycemia, electrolyte imbalance, severe motor and cognitive slowing, peripheral artery disease, sinus tachycardia, and infection. These conditions frequently require hospitalization and emergency care (1).

BMI >30 kg/m² (obese and severely obese)

Patients who are obese are more likely to experience cardiovascular complications including heart attack, heart failure, and angina pectoris. An obese and severely obese patient is more likely to have fatty liver disease including nonalcoholic fatty liver disease and nonalcoholic steatohepatitis.

Obese men are at higher risk of developing prostate, colon and rectum cancer (2). Increased body mass may also increase low-density lipoproteins (LDL)-cholesterol and decrease the levels of high-density lipoprotein (HDL)-cholesterol (often considered good cholesterol).

It may also elevate the levels of fibrinogen (accelerates the formation of blood clots) and C-reactive proteins (severe inflammation) (3). These factors increase the risk of atherosclerosis, stroke, deep vein thrombosis, and pulmonary embolism.

Elevated levels of fibrinogen may increase adipocyte inflammation and macrophage infiltration. This subsequently leads to adipose tissue fibrosis and suppressed glucose uptake. In severe cases, the patient requires hospitalization (4).

What does research suggest?

In one of the retrospective cohort studies, 1199 elderly patients (aged 65 to 75) who were overweight, underweight, and moderately obese were at higher risk of hospitalization than patients with normal BMI. Individuals who were above 75 showed no correlation between BMI and hospitalisation (5).

In another clinical study, underweight and obese patients were at higher risk of hospitalization. These patients also required hospitalization due to cardiovascular diseases (13.4 among men and 8.1% among women) and musculoskeletal diseases (12.7-12.9%). 

Almost 50% of obese men and women had an increased risk of all-cause mortality (3.2% among men and 3.8% among females) as compared to normal-weight patients. However, such circumstances were not common for overweight patients (6).

According to a meta-analysis, researchers reported that patients (n=22807) with a low BMI (underweight) were at higher risk of hospitalization due to cardiovascular diseases and chronic heart failure. The risk of cardiovascular mortality and hospitalization was minimal in overweight patients (7).

In another study, the risk of getting dementia and subsequent hospitalisation increased linearly with an increase in BMI. Around 254 patients out of 9998 men (3.4%) got a discharge or death certificate diagnosis of dementia. Underweight patients had the least risk of getting dementia (8).

In one of the clinical studies, the elevated levels of fibrinogen, blood glucose, uric acid, and cholesterol levels declined after obese patients (60 patients: 44 females and 16 males) started dieting. The same was true for extremely obese patients (4).

What factor may contribute to hospitalization with high or low BMI?

There are several factors which may increase visits to a hospital, including ageing, smoking, excessive drinking, psychological issues, and infection.


Obesity may occur at any age, but the chances of getting overweight and obese increases with age. This usually occurs due to hormonal imbalance and reduced physical activity. Ageing is associated with a high risk of abdominal obesity, insulin resistance, and metabolic syndrome (9).

Smoking and alcohol

While some studies have shown a positive relation between smoking, obesity, and hospitalization, other studies have shown that smoking decreases body weight (10,11). Similarly, studies suggest that alcohol consumption may increase BMI (11).

Psychological issues

Psychiatric crises, substance use-related complications, family distress associated with eating disorders, and medical problems directly related to eating disorders may cause an increase in BMI. Sometimes stress can decrease your weight.


According to a systemic review, several studies suggest that overweight and obese patients are prone to infections, and require frequent hospitalisation as compared to a normal-weight individual. It is more common in obese patients with other chronic conditions and the elderly (11, 12).


Medicine-related weight gain is common and frequently reported. Some medicines are known to increase your appetite, causing weight gain. For example, steroids, antidepressants, antidiabetic, and antipsychotic medication may cause weight gain equally in men and women.

Some hormonal medicines, such as Skyla, may cause weight gain due to an increased appetite. In certain cases, antidepressants, such as nortriptyline, are known to cause weight loss by decreasing the appetite.

How to maintain a healthy BMI to prevent hospitalization?

The foremost method of decreasing your BMI is to adopt a healthier lifestyle. In extreme cases, your doctor may prescribe supplements or medicines to reduce or increase your weight.

Lifestyle modifications

  • You should reduce your daily calorie intake and make a diet plan. You should not opt for crash diets as they can be harmful to your overall well-being.
  • Increase your intake of fibre. You should eat fruits, whole grains, vegetables, and proteins (fish, beans, and poultry).
  • Do not take junk food, refined grains, potatoes, high-sugar beverages, carbonated drinks, and processed food.
  • Exercise regularly under the supervision of a trained professional. 

If you are underweight, you should consume food that has high calories and is rich in nutrients. Examples include bananas, sweet potatoes, tuna, salmon, nuts, yoghurt and milk. You may try smoothies, shakes and granola bars.


The FDA (U.S. Food and Drug Administration) has approved the following medications for patients who are obese (12 years and older): 

  • Orlistat,
  • Liraglutide,
  • Phentrimine-topimerate,
  • Semaglutide, and
  • Setmelonatide (6 years and above).

As a pharmacist, I often recommend to my patients that they should control their weight through diet and exercise rather than opt for weight loss supplements or medications as drugs may cause side effects. You should make a diet plan and strictly adhere to it.

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