Eating is a very basic and highly learned activity, so problems with eating are usually seen later in the Alzheimer's disease Alzheimer's disease
A neurological disease that affects memory and behaviour. It is characterized by beta-amyloid plaques and neurofibrillary tangles in the brain. There is no known cause but genetics and lifestyle are thought to play a role..

Apart from having the appetite to eat, eating requires the recognition of food which is disrupted in agnosia Agnosia
An inability to identify perceptions correctly despite adequate function of the sensory organs (ears, eyes, skin, tongue, nose etc.)., and the coordination of motor activities, which is disrupted in apraxia Apraxia
Apraxia is defined as the inability to carry out a previously learned motor activity, despite normal function of all the component parts (muscles, nerves, joints, etc.).  For example, experiencing difficulty dressing or using a knife and fork, are often clues that apraxia is present..