Accumulation of excess body fat is easy to accomplish in a wealthy society, and it has very unpleasant consequences over the long term. The more time you spend carrying additional visceral fat tissue, the higher your risk of suffering all of the common age-related diseases in later life, the greater your expected medical bills, and the shorter your life expectancy. This is all well understood and widely ignored: the urges to eat and laze are strong in the average human.
The way in which our bodies grasp at nutrients and aggressively store any excess as fat tissue didn't evolve because it is harmful, however. It evolved because it provides an advantage to survival and propagation of the species - at least it did while we occupied an evolutionary niche characterized by unreliable access to food. When we leave that niche for one with reliably abundant nutrition, these metabolic mechanisms become a maladjustment. We have succeeded ourselves out of the obvious and ugly scenarios of famine and into the more subtle scenarios of self-sabotage. Change in our environment is now self-directed and far faster than evolution can keep up with: we are the masters of our own destiny, and what goes on in our heads becomes more important than many other factors when it comes to health, longevity, and our environment.
The pan-human profile of adiposity was shaped over our evolutionary past, reflecting ecological pressures that favored a number of unusual traits that are characteristic of our species, [widely] assumed to have been favored by the emerging 'savannah' environment in east and southern Africa. There is a tendency to consider the savannah a relatively stable environment, with our modern fast-changing urban environment generating a stark sudden contrast. An increasing volume of palaeoenvironmental data suggests that this view of past stability is very misleading ... Although outright famines might have been rare in pre-agricultural populations, and severe food shortages could be addressed by nomadism, hominin populations can be assumed to have experienced energy stress repeatedly across and within generations, resulting from various cycles of uncertainty. These include seasonality, longer-term systematic climate shifts, and extreme events such as volcanic eruptions and climatic cycles.
We can therefore consider adipose tissue as a strategy for energy storage that responds to multiple ecological stresses ... Storing energy as fat is by no means the only strategy for managing the risk of uncertainty in energy supply. A highly social organism such as humans can store energy not only in the body but also extra-corporally (in food hoards) or in social relationships. This 'redundancy' of multiple mechanisms suggests that energy risk management was crucial in the evolution of our species.
The fact that adipose tissue is the source of numerous signaling molecules highlights its role in orchestrating life-history decisions. This risk management system is, however, increasingly destabilized in many human populations. Prevailing economic policies cause individuals to be subjected to a range of 'invasive' cues favoring fat accumulation, in environments in which actual energy availability has high stability. The combination of insulinogenic diets and psychosocial stress on the one hand, and low energy demand for physical exertion, reproduction and immune function on the other, stimulates chronic lipogenesis but reduces lipolysis. At this point, high levels of adiposity become toxic and harmful to health. It is these socio-environmental cues, collectively orchestrated by our capitalist economic system, that are the optimal target for obesity prevention.
As noted above this researcher recommends efforts to be directed towards some form of intervention in society rather than new medicine; this is actually a fairly commonplace attitude, sad to say. Examples include calls for regulation of advertising or consumption - strategies well-documented to have failed miserably in wealthy societies as far back as Medieval France and ancient China. Interfering in free enterprise tends to destroy wealth - the most effective means of reducing consumption is to induce poverty throughout a society. This approach and all of its unpleasant side-effects have also been well-demonstrated, such as in the ruins produced of Russian progress and well-being during the communist era.
Freedom and the creation of sufficient wealth to produce widespread health issues go hand in hand - but are also accompanied by all the myriad benefits of wealth, such as advanced medicine, comfort, and choice. A wealthy society whose elites attain a centralized grip on power sufficient to dictate the diet and lifestyle of citizens will not long remain wealthy, as that level of regulatory and enforcement power is a cancer that spreads and kills the means by which progress happens. On the flip side of the coin, in a free society the costs of self-inflicted health issues (or insurance against those costs) are borne by the individual, serving as one counterbalancing incentive against a bad lifestyle. More importantly, the right to make bad choices and suffer their consequences is respected insofar as they hurt only the individual making them.
We evolved for a brutal environment of failure and poverty, and thus we are poorly adapted for success and wealth - but that isn't just a matter of fat tissue. Human psychology is also an issue, evolved for an age of small hunter-gatherer groups, and our instinctive attitudes towards strangers, success, inequality, and freedom cause great harm when put into practice in an age of cities and wealth. See, for example, the urge to control the actions of others that feeds the growth and centralization of regulatory states.
So at the bottom line, I think that a technological solution is the best way to dig our way out of being physically poorly adapted to success. Other strategies will either be ineffective (e.g. advocacy for better lifestyles, which would have worked already if it was going to work) or threaten the very foundations of the wealth and success that creates these unfortunate side-effects on health. There are many possible paths ahead here, some harder than others, but all basically plausible: create some form of empty-calorie bulk that can be added to any form of food; alter human metabolism; build nanomachinery or engineered bacteria to live in the gut and keep food out of our reach; and so forth. I'm sure you can think of others.