Morbid obesity is defined as clinically severe obesity at which point serious medical conditions occur as a direct result of the obesity itself.

You are morbidly obese

if your weight is over 200% of your ideal nody weight,
if you carry an over 100 lb overweight,
or if your body mass index (BMI) is over 40.

Additionally, individuals who have a BMI of 35 or greater with an existing co-morbidity (i.e. diabetes, hypertension, etc.) are also classified as morbidly obese. The term “morbid obesity” is not particularly friendly to hear, however this is most commonly used by clinicians to diagnose weight status in adults. Morbid obesity has many of the same causes and some similar risks as obesity, but you will find that they differ mostly with treatment strategies. Many obesity-related conditions accompany morbid obesity. Once an individual is considered morbidly obese, these conditions become serious health risks. These obesity-related conditions also negatively impact the quality of life for individuals and their family members affected by morbid obesity.
Almost every single organ system is affected by morbid obesity.

Patients most commonly present with one or more of the following problems:

Type 2 diabetes mellitus
Hypertension
Hyperlipidemia
Obstructive sleep apnea
Osteoarthritis
Depression
Heart disease
Gastroesophageal reflux disease
Urinary stress incontinence
Depression
Polycystic ovary syndrome
In addition, morbidly obese individuals are at a much higher risk to develop certain cancer types.

The more severe the obesity is, the higher the prevalence of developing these conditions will be. Many of these medical problems can significantly improve or completely resolve with significant and permanent weight loss. The most spectacular improvement is seen with type 2 diabetes, but not everyone will respond at the same degree. The longer these conditions persist, the more irreversible damage they cause to your body and improvement or resolution will be less likely. Current data suggest that Roux-en-Y gastric bypass is more powerful in bringing type 2 diabates to remission than either the sleeve gastrectomy procedure and this effect is just partly due to the degree of weight loss.