If you have the time and inclination read up on normalisation. A process used in RELATIONAL db design. In essence only store a piece of information once, dont repeat
that means designing tables such that you never repeat data (except keys). In practice from what you have said so far that means at least two tables
one for Persons (or clients if you prefer)
One for Oberservations(ie weighins sessions)
Persons stores everything you need to uniquely identify a client (name address phone email)
Observations stores everything relevant to a specific session where you measured the weight ( eg date weight notes/excuses?
You may need other tables as your design evolves but dont sweat it right now.say you periodically also take other measurements eg waist, chest, bicep...... some might argue theyd be in another table, but unless you have hordes of measurements leave them in observations. If you do have hordes of diaparate measuremenrs then consider the sub supertype model.
in access you are better using a form per table. If it were me fir this id yse a form for oersons and an embedded form for observations. The embedded form would be continuous rows meaning youd see multiple observations per client.
the primary key for persons coukd be either a autonumber or a made up obe something like the first 6 letters of the surname + some digits. Eg SMITH0045, FNLDWN045, HEALDE937
pk for observations likewise could be an autonumber, but probably better if its a composite of person AND date of oberservation. That way round you can never duplicate observations.
resist the temptation to dive into designing stuff in Access till you have a good idea of your requirements.
read up on good table design...
...dont use spaces in your table and column names, use underscores or capitalusation to separate words in columns. Such as DateOfBirth or date_of_birth, use consistent abbreviations eg PhoneNmb or phone_no. Tablenames in plural. Use the caption property (in the table design) to set a human readable label
understand what words Access reserves for its own use (google Accessreserved words), so dont use words like date, desc, table......
dont get frystrated or disheartened if you make mistakes, we all do.
dont loose sight of the fact your business is weight loss not system design, but enjoy the process
I'd rather be riding on the Tiger 800 or the Norton