In this case the person who was supposed to speak the truth were you. Your wife was not asking what you were doing then. So, what you should do was to inform her the two main activities you did. Here your activities were transformed into spoken form. So, all the words you used and the tone/voice modulation had great importance. But you deliberately hid a part of the truth. There was no chance of filling up of your eating sweets. If there was, and you didn't feel ANY guilty of telling so, you could say that you were speaking the truth. Otherwise you were lying. If you are deliberately leaving some ambiguity in your reply, it can be treated as a partial truth or partial lie. (In your reply you didn't leave any ambiguity. So it cannot be treated as a partial lie.)
You might argue: "In future, scientists might discover that 'consumption of sweets doesn't have any relation to diabetes', would it be a lie then?" Yes. Since your intention was not to speak the truth (you were hiding an important thing of that time), even in such a situation your reply is/would be a lie.
DECEPTION Vs LYING
The meanings given for the word 'Lie' (Noun/verb ) in some dictionaries:
A lie is something that someone says or writes which they know is untrue.
An intentionally false statement.
to deliberately tell someone something that is not true
to say or write something that is not true in order to deceive someone
Meanings of 'Deception':
the act of hiding the truth, especially to get an advantage
a statement or action that hides the truth, or the act of hiding the truth
Both in deceiving and in lying, hiding of truth happens and the liar (deceiver) gets some advantage also.
When we omit some words in a sentence sometimes they become false statements. (What happens if you omit the word 'not' in this sentence: 'All that glitters is not gold.')
Just remember how a child complains to their teachers or parents after quarreling with another one. Does the liar tell all the things he did? Truth often comes out only after questioning. So the statements that mislead someone are lies. The same thing is done in courts.
Lies mislead the sufferer (or the listener) and most often it becomes a deception if viewed from the sufferer's side. Even if the listener is not there to hear the lie, lie has been told (even in the absence of deception). That was another reason for treating your statement as a lie (rather than a deception).
To make it clear,
Suppose, a third party is listening to your conversation. Then, your lying wouldn't be a deception to your wife if she is not (at the other end) to listen to your reply. Even from the third party's point of view there is no deception in such a situation. In your particular case, you deceived your wife by telling a lie. Lie came out first and it affected her as a deception. You may say that your lying is the cause of deception. But you can never say: "Deception is the cause of your lying."
Please note: Telling a lie may be a part of practicing Dharma. I mean, if you lied and if you were asked ("Were you lying to him?"), without any hesitation you could say that you were lying. So, if no other alternative is available, in order to protect a greater Dharma, you may deviate from the maxim-- 'Speak the truth always, even if it leads to your death.' (You may refer the Mahabharata.). So you need not reveal all the secrets to all.
Since so many viewers are interested in this question, I believe this doubt also is latent in your question.