Part of the guy's problem was that he was consuming 2600 calories a day. That's 600 more than an active adult needs, and I have a feeling he wasn't all that active. If he's been eating like that for years, he'd have lots of extra weight on him, and thus once he scaled back, he started to lose weight.
You can eat whatever you want and lose weight, and for most people, the need to lose weight over the short term far outweighs any issues with nutrition, as they're doing more damage to their bodies carting around all that extra weight.
There's this perception, based on provided nutritional values, that we've got to eat all this food or we'll starve to death overnight or something, and that just feeds (ha) the perception that we've got to eat three big meals a day. Couple that with the marketing muscle of packaged food and casual dining establishments, and there's no surprise that Westerners end up consuming such huge amounts of calories.
Someone could do a study about getting fat on a vegetarian diet, it's all about the calories.