David Mendosa says you can. I’m not quite that optimistic, but probably a majority can, if they have the knowledge, discipline, and willpower. Here are some snippets from David’s blog:
You can use drugs to bring your A1C level down to normal. That’s a good thing. But this strategy does have its costs, and those costs aren’t just money out of your pocket or your checkbook. The worst of those costs are the potential side effects of the drugs.
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But some of us think we have a safer strategy of managing our diabetes without drugs. Back in 2007 I joined this group with the encouragement of a good friend of mine who is a Certified Diabetes Educator. Before that, I had 14 years of experience taking a wide range of diabetes drugs, including two different sulfonylureas (Diaßeta and Amyrl), Glucophage (metformin), and Byetta. For the past six years I haven’t taking any diabetes drugs, and yet I keep my diabetes in control with an A1C level usually about 5.4.
I had to make three big changes in my life when I went off the diabetes drugs, and they are hard at first. But now they are a routine part of my life, and I would never go back to my old ways. The changes that I had to make are those that almost everyone who has diabetes has to make. In order of importance, I had (1) to lose weight, (2) eat fewer carbohydrates, and (3) exercise more.
Read the whole enchilada. It’s brief.
Diabetic Mediterranean Diet 
Due to direct experience Dr. Parker; I am standing in your camp. While I agree that careful diet and sufficient exercise are extremely critical; they cannot do it all. I was on my 1200 calorie low carb diet and 2 miles walking for 2 years barely getting there. Once I got on metformin and got doses and timing established from looking at cgms ; my control snapped into place.
my read was that diet, exercise and meds in my case critical to arresting the mess. For folks with milder type 2 and pre-diabetes; yes I suspect diet and exercise can do the job. In very serious cases; meds – metformin, insulin and other tools may be needed. To deny that is helping no one and offering false hope. I wish people would not trot down that road oblivious to all the issues.
I don’t want anyone to feel bad about needing to take drugs after an honest effort at lifestyle modification. For that matter, if someone wants to just take a lot of medications and continue in their old potentially harmful ways, that’s their choice.
It took me 3 years to get to the point of dropping meds, after 4 years of being on them. I had to keep testing testing testing my blood daily to make sure where I was at and guide me through what I was doing.
It wasn’t my intention to cease meds but I thought I’d try it…and was surprised at the results.
There’s more to the formula diet+weight loss+exercise for diabetics and I suspect that weight bearing/HIIT type approaches are important in altering insulin activity.So ‘any’ exercise — esp aerobic — won’t suffice.
But I’d not recommend that anyone cease meds unless they know what they are doing and have confidence in their surety…nor should they do it early in their diabetic career.
Dave, you’re last sentence reminds me of a few studies in which intensive control of diabetes early on seems to help preserve pancreas beta cell function, at least in T2 diabetes. Oftentimes drugs are the best way to do that.