Here is my theory, which is admittedly not supported with facts and may turn out to be complete bullshit:
In the distant past, food was hard to come by and men had to work very hard to get it by hunting, farming, etc. This principle remained true in many parts of the world from prehistoric times through the middle ages, and even into the pre-industrial age. Due in part to this food insecurity, humans developed an instinct to consume large quantities of food when it was plentiful, as the body understood that large meals may be difficult to come by. Gorging generally did not lead to obesity however, because it was offset by periods where relatively little food was consumed.
In the industrial and post industrial age, food became more plentiful. This lead to a general decrease in the "food insecurity" issue noted above, as for the first time many people could gain access to all of their food requirements by buying it, e.g., from a grocery store. The ready availability of food likely lead to an increase in consumption by males, due at least in part to the instinctual drive to consume. Despite this increase in consumption, many males did not become obese because they engaged in significant amounts of physical labor. In essence, their work required intense physical exertion and thus burned off many of the calories that were consumed. In other words, instinct drove men to eat more because food was available, but physical exertion offset the increased consumption.
In the modern era, food is more plentiful than ever, and in a wider range of choices than ever. In particular, processed foods that are high in calories and fat have become widespread, and are attractive to large portions of the populace because of their taste and their relatively low price. This widespread availability of cheap, high calorie food has lead to another large increase in caloric intake, again fueled in part by the instinctual need to consume when food is readily available. Only this time, this increase in consumption is not offset by physical exertion. Indeed due to technological advancement, most modern men are not required to exert themselves much if at all over the course of the day. To the point that most men who do exert themselves physically do so in a gym, rather than in the course of their work. This has lead to an era where the caloric intake of a male generally exceeds the number of calories he burns over the course of the day, leading to weight gain.
For those who don't like to read -
-Due to food insecurity, human males developed an instinct to "gorge" when food was readily available.
-In the past, increased caloric consumption was offset by physical labor
-In modern times, caloric consumption has increased further due to availability of cheap processed food, while physical exertion has become "optional" for most males in the modern world, leading to an era of "caloric surplus." Nature has not caught up with the fact that males are less active now than at any other point in the history of humankind, and thus instinct continues to drive men to consume large quantities of calories despite the fact that it is no longer necessary to do so.