ABSTRACT:

Obesity has become a major public problem which is associated with increased risk to health and enhanced mortality along with increased medical costs. Prevention is obviously the first line of attack and this chapter outlines preventive strategies starting with a model which translates the energy imbalance which produces obesity into the social framework in which this occurs and where intervention must occur. Increased food intake is the major driver with reduced physical activity as a second component, modified by many other factors. Prevention beings with pregnant woman where maintaining a healthy weight gain improves the outcome for both infant and mother with diet and exercise both showing positive results. The early years of life are another important time for prevention. Studies of children have shown that exercise and nutritional quality can be improved by lifestyle intervention, but that impacting body weight change is more difficult. Reducing sugar-sweetened beverage intake and increasing water intake are two potentially useful strategies. Finally, there are many studies examining strategies for prevention of weight gain in adults as a group and in special subsets of adults with variable effect. One can conclude that prevention is the cornerstone for reducing the prevalence of obesity in pregnant women and their offspring, in children and adolescents and in adults, but that the current strategies may need to be supplemented with additional successful modalities of implementation. For extensive coverage of this area and all of endocrinology, please see www.endotext.org.

INTRODUCTION

Obesity is a worldwide problem (1) and affect more than 100 million Americans (68.5% of the adult population)(2). In the 1980s the prevalence of obesity began to rise more rapidly than before and has now reached epidemic proportions worldwide. Since 1980 it has more than doubled and In the United States data provided by the US National Health and Nutrition Examination Survey (NHANES) in 2009-2010 showed that 35.5 % (95% CI, 31.9%─39.2%) of men were obese (BMI>30 kg/m²) and 35.8% (95% CI, 34.0%─37.7%) of adult women were obese (1, 2). The National Health and Nutrition Examination Surveys (NHANES) in 2014 noted a BMI of ≥25 was present in 71.3% of men 20 years or older and in 65.8% of women 20 years or older. The prevalence of obesity (BMI ≥30) was 33.5% for men and 36.1% women combined. Females at any age are disproportionately at greater risk for obesity, and especially extreme obesity (BMI ≥40 8.3% in females; 4.4% in males). The prevalence of obesity has risen dramatically since 1980, but may have slowed at current higher than desirable levels. The prevalence of obesity among children age 3-5 is alarmingly high at 12.4% in boys and 10% in girls with higher rates in Hispanic and Blacks (3). The increase has continued in extreme obesity in the United States and is rising worldwide. This increase in the prevalence of obesity carries with it increased risks for diabetes, metabolic syndrome, non-alcoholic fatty liver, heart disease and cancer among others (4). It also has significant costs to the individual and to society (5). Clearly the “brakes” that prevented a rapid increase in obesity before 1980 are not working well enough, and new preventive strategies are needed. To select papers for this chapter the words prevent, prevention, obesity, and overweight were screened in PubMed and additional references identified from the selected papers.

FRAMEWORK FOR DEVELOPMENT OF OBESITY

Figure 1 is a model with the “energy balance” equation at the center and social and environmental factors surrounding it (4). When an individual becomes obese it is a clear sign that the balance has tipped slightly towards positive energy intake (or reduced expenditure) and that this imbalance has been present for months to years. Primary prevention of obesity would occur if strategies similar to what were in place before 1970-1980 were re-introduced and obesity rates were reversed, or alternatively if equally effective new ones were implemented. Secondary prevention is the use of techniques to prevent regain of weight in an individual who has gained too much weight as fat and then lost it. These are often also called “maintenance” strategies.

The development of obesity, that is moving the central pendulum in Fig 1 to the right in favor of a positive energy balance could occur because there is a small increase in energy expenditure, a small decrease in energy expenditure or a combination of both.

Food available for consumption and food intake, corrected for plate waste, began to increase in the US after 1970 and has continued to the present (6, 7). The extra amount of food is now estimated to be about 400 kcal/d which is enough to account for the calories needed to produce the documented weight gain (8). An alternative explanation would be a decrease in activity in the ordinary duties of the day (9). I tend to favor the rise in food intake as the major factor.

The rise in consumable food items from farms in the United States began after a change in food policy for reimbursing farmers in 1970 (10). There are several outlets for this growing surplus of food. First, it could be stored in warehouses against a future need. It could be destroyed. Or it could be transferred to storage depots on people – obesity (11). Since the growth of the population is less than 1-2% per year, the growth in food supplies was larger than needed to meet this growing population. Since we don’t see stores of food in warehouses, we have probably transferred it to the population producing obesity. As Tillotson has said “…certain of our agricultural and industrial policies have had the unintended and unforeseen consequences of increasing overweight and obesity”. Our current “preventive strategies” thus operate in a setting of agricultural and industrial policies that favor production of more food that is needed to feed the population. Surpluses of food operate in a socio-economic environment. In many groups of women this is reflected in an inverse relationship between the prevalence of obesity and the educational and income levels. (10)

Several economic hypotheses related to “food security” have been proposed. These economic factors may need to be part of the preventive strategy if we are to develop a cohesive approach to dealing with obesity around the world.

The positive energy balance that we see leading to obesity can be influenced by a variety of factors which are controlled by the individual, by the family and by society. We know that people can “consciously” control their weight by restrained eating. It is clear from the model that the individual is at the center of this system but their responses in terms of energy intake and energy expenditure are influenced by a myriad of factors over which they have little or no control. Genetics underpins obesity (11, 12, 13). There are some genes that have such potent effects on body weight that when defective obesity is almost certain. Leptin is one of the most potent (11). There are more than 90 other genes that contribute small amounts to differences in body weight accounting for less than 5% of the risk for obesity (11, 13).

Epigenetic factors, environmental influences on the fetus and early life also have important effects. For example, offspring of mothers who smoke during pregnancy or whose mother is a diabetic are at higher risk of obesity later in life and those who gain large amounts of weight (4). Duration of sleep time also affects body weight. Availability of food and its palatability are environmental factors that have significant effects that can override the controls systems for body weight. It is clear that although many of these environmental factors can be controlled by the individual, the genetic and epigenetic influences make it difficult for many people to maintain a stable body weight. Thus preventive and therapeutic strategies are needed.

STRATEGIES FOR PREVENTING OBESITY

At least 4 preventive strategies are available to deal with the epidemic: Education, regulation, modification of the food supply and changes in the cost of food energy. Education about good nutrition and healthy weight in the school curriculum would be beneficial in helping all children learn how to select appropriate foods and should be included in school curricula. Foods used in school breakfast and lunch programs should match these educational messages.

However, it is unwise to rely on educational strategies alone, since they have not, so far, prevented the epidemic of obesity. The program of knowing your BMI initially instituted on a state wide basis in Arkansas may have helped that State to reduce the upward trend in obesity. Regulation is a second strategy. Regulations to provide an improved food label would be one good idea. Better regulations on appropriate serving sizes and caloric value that would be easy for the public to use might be part of the information provided by restaurants on their menus. This is now required in New York City and if effective may spread around the country.

Modification in some components of the food system is a third and very important strategy. Since the energy we eat comes from the food we eat, we need to modify this system to provide smaller portions and less energy density. One approach is to use differentiated food taxes to promote healthy diets. This is the approach New York State is trying with its tax on soft drinks introduced in 2007, and has been urged by a group of prominent nutritional scientists (15). This strategy has been argued both at the academic level (16, 17, 18), and at the policy level. It may be that economic tools that will shift food choices using cost is the “fluoride” for treating the epidemic of overweight that is described below.

Some years ago, I proposed that the best strategy for prevention of obesity may be modeled after the use of fluoride for prevention of dental caries (19). The addition of fluoride to the water supply had a more profound effect on the incidence of dental caries than brushing and flossing teeth. Brushing and flossing are like diet and exercise. They both require commitment on the part of the individual. Adding something like fluoride to the water supply doesn't require any commitment. Increasing the price of oil may be one such strategy. Between 1940 and 2005, Pollan pointed out that the number of calories from petroleum (oil) used to produce food energy has risen dramatically. In 1940 it was 0.4 cal of oil for each calorie of food energy. In 2005 it had risen over 20 fold with 10 calories of oil needed for each calorie of food. These calories come from the petroleum products used to make fertilizers, to transport of food, to process and package food, for pesticides and so on. If oil prices rise significantly, this will shift the use of oil for food and shift our consumption patterns (20).

INCREASING PHYSICAL ACTIVITY AS A FOCUS FOR PREVENTION

An overall increase in physical activity would increase energy expenditure and is one strategy for prevention of obesity. One assumption of such a strategy is that activity may have decreased during the time that the epidemic of obesity developed. This is difficult to establish, but a recent publication using total daily energy expenditure in a small number of individuals (some 300) measured over years (74). This strategy would be appropriate, whether there has been a decrease in energy expenditure or not, and the data on this question is unclear. In contrast, Church et al (8) have presented data showing that leisure activity has declined as the obesity epidemic has moved ahead. Altering the “built environment” such as side-walks and shopping centers is one way to do encourage more physical activity (61). However, there is a 30-40 year lag between initiation of changes in architectural land use and real changes in configuration of side walks, making these approaches unlikely to impact this problem in the foreseeable future.

How much has our daily activity level changed? To examine this question Cutler et al (75) examined this problem levels of activity in various tasks from 1965 to 1995, which covers the period before and to the peak of weight gain. They found that over the 30 years from 1965 to 1995 the major changes in activity have been a decrease in household work and an increase in recreation and communication. These are relatively small compared to the proportion of the daily routine which is spent in paid work and in personal needs and care. We thus think food intake is a more viable strategy for combating the obesity epidemic.

Work places are another place where prevention and intervention can occur. In a review of worksite nutrition and physical activity programs Anderson et al (76) noted modest improvements in employee weight status at the 6-12-month follow-up. Based on 9 randomized controlled trials, there was a loss of 2.8 pounds (-1.3 kg) (95% CI=-4.6, -1.0 weight loss) and a decrease of 0.5 (95% CI=-0.8, -0.2) BMI units based on six RCTs. The findings were applicable to both male and female employees, across a range of worksite settings. Most of the studies combined informational and behavioral strategies to influence diet and physical activity; fewer studies modified the work environment (e.g., cafeteria, exercise facilities) to promote healthy choices. This is an area of potential future advance.

The nutrition-transition in China provides an interesting example of how the modern way of life makes preservation of physical activity so difficult (77, 78). As recently as 20 years ago, the bicycle was a major mode of transport for Chinese. This is no longer the case. The automobile and public transport systems are relegating the bicycle to museums. Whether understanding the need for people to move can provide a rescue strategy for weight gain is doubtful.

USE OF SOCIAL MARKETING

One element in trying to combat the obesity epidemic is to

focus on the needs of selected groups – so-called social marketing. The idea is to provide focused messages targeted at specific sub-groups. Another approach is to focus on specific food groups. The program by the National Cancer Institute to increase Fruits and Vegetable consumption through the “5 A Day for Better Health” program is an example of this idea. Although we would all agree that this is a desirable approach, its effectiveness in changing the consumption of fruits and vegetables has not been overwhelming (79).

SUMMARY AND CONCLUSION

Efforts to prevent obesity or to reverse components through changing lifestyle have focused on both adults and children and well as worksites. Although some changes can be documented in these studies, the net effects have been small and the epidemic has continued to move ahead. The role of economic incentives have received less exploration, but may be more promising as a way to halt this epidemic.

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