What's wrong with this query:
INSERT INTO Users( weight, desiredWeight ) VALUES ( 160, 145 ) WHERE id = 1;
It works without the WHERE clause. I've seemed to have forgot my SQL..
Answer
MySQL INSERT Syntax does not support the WHERE clause so your query as it stands will fail. Assuming your id column is unique or primary key:
If you're trying to insert a new row with ID 1 you should be using:
INSERT INTO Users(id, weight, desiredWeight) VALUES(1, 160, 145);
If you're trying to change the weight/desiredWeight values for an existing row with ID 1 you should be using:
UPDATE Users SET weight = 160, desiredWeight = 145 WHERE id = 1;
If you want you can also use INSERT .. ON DUPLICATE KEY syntax like so:
INSERT INTO Users (id, weight, desiredWeight) VALUES(1, 160, 145) ON DUPLICATE KEY UPDATE weight=160, desiredWeight=145
OR even like so:
INSERT INTO Users SET id=1, weight=160, desiredWeight=145 ON DUPLICATE KEY UPDATE weight=160, desiredWeight=145
It's also important to note that if your id column is an autoincrement column then you might as well omit it from your INSERT all together and let mysql increment it as normal.