What is the basic reason that achalasia patients loose weight? is it because they start eating less or is there another underlying reason?

Difficult Swallowing: Weight loss associated with Achalasia is usually due to difficulty swallowing. Patients often experience the sensation that swallowed material, solids and liquids, gets stuck in the chest. Some may compensate by eating more slowly and by using maneuvers, such as lifting the neck or throwing the shoulders back, to improve emptying of the esophagus. If oral intake is decreased, weight loss results.

Malabsorption: Achalasia is a relatively uncommon disease usually of the muscles of the lower esophageal body and lower esophageal sphincter. This prevents relaxation of the sphincter and an absence of contractions, or peristalsis, of the GI segment. This results in very slow movement of food in the GI tract. Achalasia can also occur at any point in the GI tract, causing poor absorption, & wgt. loss.