People also consume many more calories in places where they didn't in the past. For instance, a soy latte from Starbucks has 210 calories. If you don't change anything in your diet or exercise habits and drink one of these every work day, you'll gain 15 pounds in a year.
I don't know this for sure, but if I recall correctly people eat fewer calories now than they did in the 70s. I know it's not a dramatically different number either way. It's the composition of the calorie that has changed. I'm firmly convinced of the fat vs starch theory. People eat much less fat and oils now and eat more starch.
I doubt I'd recommend replacing fat with carbohydrates, but you're correct in that sugars (starches/carbohydrates break down into...) cause the body to store fat (more specifically, the elevated insulin levels that accompany this).
Regarding weight loss: I work & exercise with a variety of body types (these body types have people names too!), and, within this small sample, I've found that the dominating factor in overall weight is diet, not exercise.
Essentially, exercise controls muscle tone and how "tight" the skin is, while diet seems to control the overall body shape.
