For me, 3 TS meals a day would be too much food (and I like to eat well on vacation).
Let me give you a couple of scenarios from our most recent DxDP trip:
On our first full day at WDW (at MK), we had breakfast (8:15 ADR) at CRT (I cleaned my plate but didn't go for seconds). Later that morning (at around 11 am), I used a snack credit for a funnel cake at Sleepy Hollow. Then, around 2 pm, I used another snack credit for a Dole Whip at Aloha Isle. We had dinner that night at Artist Point. I was able to eat all my dinner entitlements (bread, appetizer, entree, dessert) but only because the meal was really good. If I'd eaten lunch that day (regardless of how early the ADR), there's no way I'd have been hungry enough for the whole dinner.
On our next day (at HS), I used a snack credit in the morning (at our resort) for a yogurt parfait. For lunch, we had the earliest possible ADR (11:30) at 50's PT. I ordered the crabcake appetizer (small), fried chicken (asked for only breast pieces, which means they give you less), and used my dessert credit for a PB&J milkshake. Later, at around 2 pm, I used a snack credit for a Mickey Bar. We had dinner that night at Citricos. I was again able to eat all my entitlements, but started feeling really full about halfway through the entree and really struggled to finish the dessert. If I'd had breakfast (instead of just the yogurt parfait) there's no way I'd have finished dinner.
After that, I realized that I needed to be more disciplined in my dining (and this was eating just 2 meals a day). On subsequent days, we had breakfasts at Tusker House, Crystal Palace, and Cape May and I was careful to only take one pass at each buffet (even though I really wanted to go back for seconds). I also started having somewhat less caloric snacks (often just having bottled water for the afternoon snack). This enabled me to enjoy the dinners much more (was still very full at the end). But if I'd have thrown a lunch into the middle of those days, even with the earliest ADR, there's no way I'd have made it through the dinners.
Anyway, that was my experience.