Means that you, or someone/something else has gained weight for no obvious reason.
You can, but unexplained weight loss can also mean that your cirrhosis has progressed to liver cancer.
If you mean McDonalds then yes it does help you gain weight.
Skipping a meal doesnt necessarily mean that you will gain weight, but it will make you want to eat a little more than regular to make up for that lost meal. So that's where, I would think, people would get the idea that skipping meals make you gain weight.
An unexplained phenomenon is a thing that someone or a group of people saw. It is unexplained when their is no logical reason as to why it happened. UFO's serve as examples to unexplained phenomenons.
It means you did it wrong.
Abnormal Weight Gain
First signs of pregnancy
im assuming you mean solpadol, the pain reliever. While this does have side effects, none of the side effects include weight gain.
It depends what you mean by side effects. However a balanced diet and proper exercise is the best way for a normal person to gain weight
If your cat eats so much but does not gain weight it may mean that your cat is diabetic and should be taken to a veterinarian.
Means growing heavier, usually through becoming fatter,
The unexplained is generally considered to mean the same as anomalous phenomena. Examples of this are UFO sightings and crop circles.