I think we have all been through the stage of being ashamed of our obesity and admitting it is an issue to others, even those closest to us who should be there to support us, think.
I ordered before telling dh and hid in the fridge for a couple of weeks before I was ready to use. By the time I was ready to use I was also more knowledgeable on the medication and also ready to tell him and ds. The only other people I have told is a couple of family members I am very close to. I haven't told any of my siblings.
Obesity is a chronic disease. He may find it easy to maintain his weight. For some people whether it is physiological or psychological you cannot do the same and it is impacting your health. I explained this to dh, with all the relevant information. You are not to blame and should not feel or be made to feel ashamed.
You are being proactive at protecting your health by looking into tools that can help you. You have (hopefully) fully researched the medications available and balanced the risks between obesity and the taking the medication and you can explain these to him.
He can be concerned for you, he can have questions about how they work and the risks, or even the financial commitment. You are not being unreasonable to expect him to understand obesity is a serious health risk and expect him to support you the same way you would support him if he had a health condition. You should also expect him to respect your privacy and not discuss with anyone else.
When I was thinking about how/whether to tell my dh, I also thought, if dh had a health condition and kept it from me I would feel upset that he felt he couldn't talk to me about it.
Obviously up to you who you tell and it may take sometime for you to get to that point, but do think seriously why you need to hide it from your dh. If you have any unpleasant side effects (fairly common in first weeks/going up doses) you will need to lie to him about them. If you have serious side effects (very rare) he can help you.
Possibly show him this -
s