The abs seem to grow more in strength and endurance, rather than size. Read on this, folks, google it. I am not "necessarily" saying they dont grow, What I am saying is to compare the "type" of ab growth to the other parts of the body is comparing apples to turnips--though they are the same (if one understands what I am getting at).
In order to answer this persons question, we have to ask more questions on what he wants.
The thread starter wants a bigger waist........I would like to ask why? What does your current ab core look like? What condition of development are your legs and upper body? Are you willing to change your diet to obtain your goal?
What exactly is your goal? Be more specific. Have you lifted weights before, if you have, how long?
At present its too general to give specific advice.
Your info was misleading Rip from what I mentioned before, and for this:
What if this guy was eating like a bird? Boy those 1,000 situps and weighted ab exercises are sure gonna pack on the mass.......not happenen. You must ask him about his diet. And, those 1,000 situps and weighted ab exercises even if he was eating like an elephant will not pack on the "muscle mass" in the ab area.........not happenen. The only area, that I may agree may come close, but not quite, to the other muscles of the body in growing MAY be the obliques (or the lower sides near hip bone).
You were focusing on the ab routine (and wrong), and the real focus should be on the diet for mass gains, and there is no arguement over that.
If abs clearly showing are NOT the goal, then implementing a caloric surplus coupled with an overall weight training is the answer to a bigger waist. You must learn your MT line (though fitday or other reputatable site) based on current activities, and then go over a reasonable amount, and watch for the feed back on this surplus, and adjust accordingly. AND, EAT CLEAN GOOD FOOD.
One the exercise portion, I suggest overall weight training. I can give some basic advice in general terms, but I would like to know if you have worked out before and how long. Currently, and subject to change, I would reccommend the (6-7) to (10-12) rep range in reps and compound movements for the upper body. This is more of a basic starter range, without knowing specific facts about you. Going heavy doesnt necessarily work for everyone, but in general terms, going heavy (smart wise) for mass (with surplus calories) wont be a bad idea.
I also suggest, squats and dead lifts. The squat doesnt even get mentioned in the breath as an ab torso exercise. However, I assure you, if you ever get sore from the squat when doing them right, you WILL find out what muscles are at work. This MUCH touted exercise, does more for the body and cant be under estimated. The same for the dead lift. Have you done these before? If so how long? You see asking this question will determine his present state, and then one can suggest off of this.
If you havent done them before, start out light, and get the form down, and then do them reletively heavy, but more in the moderate-heavy range to get started.
I have an idea on the back, and yes back exercises. especially the lower back end, but give more information on what you desire.
Im not even going to mention ab exercises in the SAME BREATH as overall weight training, because HIS goal can be reached with overall weight training and more importantly, with a caloric surplus, and get the job done.
And an ab routine (2 to 3 days a week, or even less, on a progressive resistance manner), is all good but, I would argue, one could get it done WITHOUT --direct---ab training, but through indirect torso training when done right.
Caloric surplus (calculated right) with overall entire body training will give him his goal he seeks, NOT AB exercises.
As a side thought: I would include db weighted side bends for obliques (near hip bone). With the small amount of added fat on top (brought on my caloric surplus), and since they tend to respond, in general, better than the abs core in growth, this should make your waist wider as you wish)
Im nearing 46 and I can promise you I didnt get my abs through the ab exercises--its was diet number one. Its the same on either side of the equation: gaining or losing.
If you are a personal trainer, why are you reccommending 1,000 sit ups, LOL. We have other trainers on this site, I absolutely respect, like stoutman, I KNOW he would NOT reccommend 1,000 situps, and would ask in his response about the diet, and other questions more taylored. He hasnt been around lately, but I assure you, (dont blast me steve, lol), he would not agree with you.
By the way, thanks for the pic, you have done a good job.
He needs to give more information.