**3. Interventions to reduce obesity**

What has changed is not the brain, but the environment [23, 26]. The anthropological record reveals that the switch from hunting-gathering to farming as the primary source of food (with a greater reliance on carbohydrates than lean meat) began 10,000 years ago [49, 50]. The use of salt (and probably herbs and spices) to flavor foods dates back to at least the Bronze Age [51], but sugar was not widely available until the 1500s [52]. However, it was the industrialization of the food supply (i.e., the processing and distribution of food) in the last half of the twentieth century that has had the most dramatic impact on how today's humans eat [26, 53, 54].

The availability of high-calorie foods (e.g., carbohydrates and fats) has markedly increased in the United States since the 1970s [55]. One of the most obvious changes that began in the 1970s, at about the same time as the prevalence of obesity began to rapidly increase, was the proliferation of fast-food restaurants. McDonald's opened in 1955, had 1000 restaurants in 1968, and today has over 36,000 restaurants in over 100 countries. Burger King opened in 1954, had 275 restaurants in 1967, and today has 13,000 restaurants in 79 countries. Wendy's opened in 1969 and today has over 6850 restaurants. Similarly, today, Kentucky Fried Chicken has over 19,400 restaurants, Pizza Hut over 11,000, Taco Bell over 6500, Arby's over 3300, Chick-fil-A over 1950, and Church's Chicken nearly 1700 restaurants. Most of them have drive-up windows. Altogether, sales at the US fast-food restaurants increased from \$16.2 billion in 1975 to about \$110 billion by 2004 [56] with a corresponding increase in American's proportional consumption of calories in the form sweetened drinks and such foods as cheeseburgers and pizza [57, 58]. Add to fast-food restaurants an increase in cafeteria and full-menu restaurants, convenience stores, and dispensing machines, and the end result is an obesogenic environment: a high density of high-calorie food sources that require little energy expenditure for consumers to access.

Numerous studies have found a positive association between the geographical density of fastfood restaurants and prevalence of obesity [59–64] or obesity and the frequency with which individuals eat at restaurants [65–70; see also 71]. Compared to normal-weight persons, overweight and obese individuals consume larger meals when eating away from home [72]. Many studies have also found that when groups of people move from areas of the world where the prevalence of obesity is low to an obesogenic environment (e.g., the United States), they gain weight and eventually display the same prevalence of obesity as is found among those who were born in the obesogenic environment [73; see 24 for a review]. Freshman students often gain excess weight during the first few weeks of attending college [74]. One third of American adults may not (yet) be overweight, but many of them live in areas (e.g., very rural)

As with any genetic trait (e.g., height), there is diversity, and some people are more obesity prone than others [18, 75–77]. Obese individuals are less responsive to homeostatic satiety mechanisms [76–78] and are much more responsive to external feeding stimuli than are normal-weight people [7, 24, 27, 77, 79]. The latter includes not only the taste and texture of food but also social cues (e.g., number of others eating, the sight of and variety of foods, portion size, time of day). Compared to others, obese individuals have a strong tendency to discount

Studies with twins reveal that appetite (responsiveness to food cues) and satiety responsiveness are highly heritable behavioral characteristics [27, 76, 77, 79], as is cognitive restraint,

delayed food rewards in favor of immediate rewards [80–83].

that are not obesogenic.

60 Adiposity - Epidemiology and Treatment Modalities

As the prevalence of obesity has increased, the number and variety of weight loss programs have increased almost exponentially. Using the key terms "obesity," "humans," and "weight loss," Medline indicates 67 publications in the time period 1965–1974 and 13,904 publications from 2006 to 2015. Today, Americans spend over \$60 billion a year on attempts to lose weight [88]. The medical cost of treating adult obesity in the United States is between \$147 and \$210 billion per year [30].

All diets work—in the short run. They may differ in the types of food recommended to eat, but when fewer calories are consumed than expended, the result is weight loss. Most overweight and obese individuals have successfully dieted for a few weeks and many for a few months, but in the long run, the success rate of behavioral therapies alone has proven to be very modest at best. Most dieting individuals do not maintain their weight loss [89, 90]. This was first noted nearly 60 years ago:

"Most obese patients will not remain in treatment. Of those who do remain in treatment, most will not lose significant poundage, and of those who do lose weight, most would regain it promptly" [91, p. 87].

Results with pharmacologic treatment of obesity alone have proven equally disappointing [92– 94]—individuals achieve meaningful weight loss only when the medication is accompanied by additional lifestyle interventions [95] and maintain the weight loss (usually modest) only as long as they remain on the drugs [96]. Mean excess weight loss for extremely obese individuals who have undergone bariatric surgery is only about 50% ([97]; see [98, 99] for reviews), with many others losing substantially less weight (see [100] for a review), and still others eventually regaining much of their excess weight [101]. (Note: the author is not underestimating the health benefits of a 50% loss of excess weight.)

Long-term weight loss is, at minimum, a two-part process: (1) initial weight loss and (2) relapse prevention. The relapse rate is high because it is normal for the evolved brain's reward circuitry to direct humans to overeat when good-tasting/high-calorie foods are available [23]. Regardless of how weight loss is initially achieved (diet, pharmacology, and/or surgical intervention), sending the client back into an omnipresent obesogenic environment with a few behavioralcognitive instructions (e.g., counting calories; monitoring carbohydrates, fats, and portion size; eating slowly; more exercise) has not worked long term for most people [89–91, 101].

For many individuals who have recently lost weight, relapse prevention will mean, in part, learning how to reduce food cue responsiveness [76]. Obese individuals are more easily tempted by pleasant-tasting food when it is easily available than are lean individuals [8], an aspect of the greater responsiveness to external stimuli. Today, the obesogenic environment is omnipresent—in the workplace, in schools, throughout the community, and in the media. Weight-loss interventions have failed because, historically, they have put the responsibility almost exclusively on the individual. In 2012, the Institute of Medicine [102] concluded that government, industry, the community, the media, and medicine must be part of a multifaceted approach (e.g., an increase in social marketing, as was done with smoking) to help individuals address how to limit and deal with an ever-increasing obesogenic environment [22, 26, 88, 103– 105].
