Create the tool that users can use with minimum time spending. Eat to live, not live to eat, right?
Application should not force you add a lot of information. All fields are not required.
User added only total calories per meal - great. User added only info about what products were in meal - it's ok. User even can set total calories per day by himself. We need to create maximum flexibility.
Application should be allowed from any devices, online and offline. User has to have ability to add info anytime anywhere.
User should have ability to access addition information but not in the front. Our potential user is advanced user.
This is long term application. Ideally for all your life. It should be super easy and comfortable to use.