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ORIGINAL RESEARCH COMMUNICATION |
1 From the Center for Human Nutrition, Denver, CO. 2 Reprints not available. Address correspondence to JO Hill, 4455 East 12th Avenue, University of Colorado, Denver, Denver, CO 80220. E-mail: james.hill{at}cudenver.org.
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ABSTRACT |
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INTRODUCTION |
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On an individual level, treating established obesity through lifestyle modification has proven to be extremely difficult (12), and those few who do succeed have had to make dramatic changes in their diet and physical activity patterns (13). Most people who achieve weight loss through lifestyle modification regain most of the weight lost over time (12, 14).
On a population level, efforts have been directed toward either producing weight loss or preventing those who are not obese from becoming obese. Even though population efforts aim for smaller behavioral changes, there is little indication that these efforts have produced any sustainable changes. Given the complexity of the situation and the many factors promoting weight gain in the population, many consider the situation to be hopeless and predict that most of the population will eventually become obese (15).
In 2003, Hill et al (11) published an article in Science suggesting a paradigm shift in prioritizing strategies to reverse the global epidemic of obesity. These authors suggested that efforts should be focused first on promoting small lifestyle changes and not on producing weight loss or preventing obesity but on eliminating or reducing the gradual excessive weight gain that is occurring in people of all ages. Over time, such efforts can lead to observable reductions in obesity rates. Although previous efforts at promoting small behavioral changes have been made, this article is the first to suggest that a comprehensive approach involving small changes in both diet and physical activity can be effective at addressing the global epidemic of obesity.
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RATIONALE FOR CONSIDERING A SMALL-CHANGES APPROACH TO ADDRESSING OBESITY |
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There are several reasons why a small-changes approach might be an effective way to address the obesity epidemic.
100 kcal) and simple food substitutions, such as a diet soda for a regular soda [saving 150 kcal per 12-oz (340.2 g) serving] would be more sustainable than efforts to achieve the larger changes in diet and physical activity required for permanent weight-loss maintenance. This is not to say that small lifestyle changes will have a greater impact on body weight than will smaller ones but rather that small sustainable changes are better than larger ones that cannot be sustained. 100 kcal/d. The energy gap was estimated from the average weight gain in US adults, which was determined, using longitudinal and cross-sectional weight data, to be 0.4–0.9 kg/y. This gain would result from an average accumulation of body energy of 15 kcal/d. The authors assumed that excess energy intake is stored with 50% efficiency (a very conservative assumption), so that the average energy gap in the population is 30 kcal/d. The average accumulation of excess energy at the 90th percentile for weight gain was 50 kcal, producing an energy gap of 100 kcal/d. Since the publication of the Science article, the small-changes approach has been widely embraced. For example, the US Department of Health and Human Services launched a small-changes initiative that included television and radio commercials and a website (www.smallstep.gov; accessed 13 October 2008). The small changes message was promoted by the US Surgeon General (www.surgeongeneral.gov/priorities/prevention; accessed 1 December 2008). A nonprofit initiative, America On the Move (www.americaonthemove.org; accessed 13 October 2008), was formed to promote the small-changes approach to modifying diet and physical activity. Through its Partner with My Pyramid Corporate Challenge, the US Department of Agriculture enlisted 81 companies to make product, packaging, and promotion changes to help consumers make small changes consistent with the Dietary Guidelines (www.MyPyramid.gov; accessed 2 December 2008). Groups such as the American Diabetes Association, the American Heart Association, and the American Cancer Society recommend the small-changes approach, as do many other public health organizations.
The food industry has embraced the small-changes approach by addressing portion size. Offering snacks in 100-kcal packages has become extremely popular and is based on research showing slightly higher energy intakes when food is presented in large rather than small portions, although the impact of packaging snacks in smaller portions on energy intake of the population is yet unclear.
In short, the small-changes strategy is increasingly being embraced by many of those interested in addressing the obesity epidemic. The purpose of this article is to evaluate the scientific evidence supporting the feasibility and effectiveness of this strategy for addressing the global epidemic of obesity. An additional intent is to consider how this approach could be used in modifying environmental determinants of energy intake and physical activity. In this review, we consider the following specific questions:
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CAN THE ENERGY GAP HELP IN DEVELOPING STRATEGIES TO ADDRESS OBESITY? |
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15 kcal/d) and is in contrast with the energy gap that is created by cumulative weight gain leading to obesity. The energy gap provides an estimate of the degree of behavioral change that would be required to achieve a specific weight outcome. For example, the energy gap required for an obese individual to return to a healthy BMI would be large (16). This is because there is a cumulative increase in body weight as obesity progresses, which leads to increased energy costs. The energy gap for preventing weight gain is small because it estimates the degree of behavioral change required to not gain any additional weight, regardless of whether the person is lean, overweight, or obese.
The energy gap for weight loss can also be estimated. Energy requirements are higher in the obese, but decline with weight loss because of declines in resting energy expenditure and reductions in the energy cost of physical activity (17). The energy gap required to produce and maintain weight loss would be significantly larger than the energy gap required to prevent weight gain. We used data obtained in a whole-room calorimeter (JO Hill, HR Wyatt, unpublished observations, June 2007) to estimate that the energy gap to maintain a 9–14-kg weight loss in obese subjects would be 175–250 kcal/d and that the energy gap to maintain an 18–27-kg weight loss would be 325–480 kcal/d (Figure 2). This large energy gap created by weight loss illustrates why large behavioral changes are required to achieve and maintain reductions in body weight in obese individuals. It is important to emphasize that these values are applicable to the obese population and should not be extrapolated to whole populations because there may be some metabolic adaptations to established obesity.
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0.5 kg/y over 5 y and resulted in the daily accumulation of energy of 10 kcal/d. More recently, Zhai et al (19) estimated the energy gap in the Chinese population to be 45 kcal/d. Wang et al (20) estimated the energy gap to be 110–165 kcal/d among children by investigating the difference between the actual and optimal trajectory of weight gain. In a longitudinal study that compared growth in children of 2 lean parents with growth in children of 2 obese parents, Goran et al (21) found that the average excess accumulation of body energy between groups was 25 kcal/d, or 50 kcal/d, based on the assumptions of Hill et al concerning energy storage.
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60 y of age. From 1971 to 1992, the average weight gain of those aged <60 y ranged from 0.25 to 0.54 kg/y. Ebrahimi-Mameghani et al (24) followed a Scottish population for a total of 9 y and found that only 20% of the population remained at a stable weight. Approximately 42.2% of the population gained >5 kg, and 17.6% of the population gained >10 kg during the 9-y study period. Berg et al (25) examined a population of men and women in Sweden and found a mean body weight increase of 3.3 kg for women and 5 kg for men over the 17-y study period. A study in Chilean women aged 40–53 y found an average weight gain of 3.8 kg over 5 y (26).
Several studies have shown that some groups are gaining weight at a much higher rate than the general population. In these populations, the energy gap is >100 kcal/d. Levitsky et al (27) followed a sample of students during their first semester in college. The results showed a mean weight gain of almost 2 kg in the first 12 wk of college, which constituted an energy gap of 367 kcal/d. A study conducted by Butte et al (28), which followed a large cohort of Hispanic children (4–19 y of age) for 1 y, found that the mean weight gain was significantly higher in overweight children (7.5 kg/y) than in nonoverweight children (4.4 kg/y). The energy gap was 130 kcal/d more for overweight Hispanic children than for nonoverweight Hispanic children.
In summary, the available data suggest that many populations are gradually gaining weight, which is being fueled by a relatively small difference between energy intake and energy expenditure. Put simply, on average, most people are consuming only slightly more calories than they are expending and, consequently, are gradually gaining weight at an average of 0.5–1 kg/y.
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IS THERE EVIDENCE TO SUGGEST THAT A SMALL-CHANGES APPROACH CAN BE EFFECTIVE AT REDUCING OR STABILIZING OBESITY RATES? |
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26% of this population met even the 30-min/d physical activity level recommendation. Moreover, this number has not changed over the past decade. It is clear that guidelines that set large behavioral goals for physical activity have not been successful.
Alternatively, Hill et al (11) estimated that an extra 2000 steps/d would be sufficient to increase energy expenditure by 100 kcal/d and that this simple change could stop weight gain in most adults. These authors further suggested that pedometers could be used as tools to allow people to set and monitor physical activity in steps/d. Before 2003, several studies had been published that used pedometers to measure physical activity, but a Medline search found that only 4 of these studies used an increase in the number of steps per day as a physical activity intervention. Since 2003, >30 studies that used an increase in the number of steps per day as a physical activity intervention have been conducted. A review by Ogilvie et al (33) provides the details and outcomes of these interventions. Bravita et al (34) reviewed 26 studies (n = 2767 subjects) in which pedometers were used as tools to increase physical activity. Pedometers work because they provide physical activity goals that are simple and measurable. The average increase in steps per day was 2491, which represented a 26.9% increase in physical activity over baseline. Most people can obtain this type of increase by walking for 20–25 min. Such an increase would be effective for most people to achieve the recommended physical activity level of 30 min/d. Moreover, this increase of 2491 steps/d, or 20 min/d of walking, was associated with a slight decline in BMI (0.38). The main point is that 20 min of walking is a small behavioral change that was achieved and was sufficient to prevent weight gain.
Other small-changes approaches to increasing physical activity have been shown to be effective. Dolan et al (35) evaluated the impact of prompts to take the stairs instead of the escalator. These researchers reviewed 8 studies and found that the mean (± SD) increase in stair usage was 2.8% ± 2.4%. It was projected that a 2.8% increase in stair usage could result in the prevention of a weight gain of 300 g/person per year in new stair users. The authors concluded that this strategy could have a slight impact on reducing the national prevalence of obesity. However, it should be noted that if the impact of the environment worsens, additional changes might be required to avoid weight gain.
Another small-changes approach is the Take 10! Program, which is aimed at integrating increased energy expenditure into academic curricula. Caloric expenditure with this intervention ranges from 25 to 37 kcal/10-min session (36). Participating in 5–10 Take 10! sessions per week would burn an additional 150–300 kcal during this period. This small change could have a big impact on energy balance and weight maintenance in the school-aged population.
Effects of large compared with small changes on improvements in diet
Efforts to achieve large changes in the diets of Americans have not been widely successful. The More Matters program (formerly known as the 5-a-Day program) has promoted the consumption of 5 servings of fruit and vegetables/d since 1991, with only modest success. The percentage of Americans who know that they should eat 
5 servings of fruit and vegetables/d has increased from 8% to 20%, but the consumption of fruit and vegetables changed little from 1994 to 2005 (37).
Americans were told to make big reductions in dietary fat intake in 1980 and in the early 1990s (38, 39). Although much was made of the resulting decline in the percentage of calories from fat eaten, the total fat consumed (in g/d) declined very slightly in the mid-1980s but actually began increasing in the late 1980s (40). The percentage of calories consumed from fat declined because of an increase in total energy intake (40). Additionally, efforts to promote big reductions in dietary carbohydrate during the late 1990s and early 2000s were not sustainable, as evidenced by a decline in several formerly very popular low-carbohydrate diets.
Some big changes in diet have been successful. One such change has been an increase in the consumption of reduced-fat milk; however, this change has occurred over 35 y (41). Another successful big dietary change has been recent efforts to eliminate most synthetic trans fatty acids from the US diet. This change may be working largely because it does not require major behavioral changes on the part of the consumer. The changes are being done by the food manufacturers and by restaurants, which have reduced their use of partially hydrogenated fats. Consumers who seek to eliminate trans fatty acids can do it with little or no sacrifice of taste or convenience.
The small-changes approach as a single strategy to reducing energy intake in populations has not been directly tested. However, a great deal of research suggests that small changes in specific components of the diet could produce small but important changes in energy intake without the need for conscious energy restriction. For example, Donahoo et al (42) found that energy intake will decrease by 20 kcal/d with each 1% decrease in the percentage of fat in the diet. Perhaps small changes in dietary fat would be more sustainable than larger ones. Similarly, small reductions in portion size can produce reductions in energy intake without stimulating hunger (43–46). Consumption of sugar-sweetened beverages in the United States has increased from an average of 222 to 458 kcal/d over the past 25 y (47). Reducing the consumption of caloric beverages has been found to decrease total energy intake (48), so there may be merit in recommending small reductions in the consumption of these products. Studies have also shown that fiber supplementation can reduce energy intake by 15–20% (49).
Reducing the energy density of certain foods is a strategy that can be achieved with reductions in fat or sugar intake (provided these macronutrients are replaced by ingredients with fewer calories, such as protein or carbohydrate in the case of fat) or with increases in fiber, water, or air. The advantage of this approach is that calorie intake can be reduced without a decrease in serving size. Prentice and Jebb (50) reviewed the published data on energy density and energy intake and concluded that the evidence is clear that energy intake increases directly with increases in energy density. Rolls et al (51) consistently found that reducing energy density produces small reductions in energy intake in short-term experiments. They estimated that a reduction of 0.1 kcal/g in the energy density of the diet produces reductions in energy intake of 110 kcal/d in men and of 82 kcal/d in women. The strategy of reducing energy density seems to reduce energy intake in children as well. Leahy et al (52) found that reducing the energy density of an entrée served to children reduced energy intake from that entrée by 25% and total intake from the meal by 18%.
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HAS THE SMALL-CHANGES APPROACH BEEN USED SUCCESSFULLY TO REDUCE OR PREVENT EXCESSIVE WEIGHT GAIN? |
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The most direct evidence for the ability of the small-changes approach to reduce or prevent excessive weight gain comes from Rodearmel et al (53, 54), who used a family-based small-changes intervention in families with at least one child who was overweight or at risk of overweight. These researchers tested the efficacy of the America On the Move initiative, which advocates an increase in walking by 2000 steps/d and reducing energy intake by 100 kcal/d. In one study (53), the intervention families were asked to make 2 small changes: 1) to consume cereal for breakfast and 2) to increase physical activity by 2000 steps/d over baseline. After 14 wk, the increase in BMI-for-age in the target children was significantly less in the intervention group than in the control group. Mothers in the intervention group also experienced a favorable change in BMI.
In a second study conducted by Rodearmel et al (54), the intervention consisted of 1) reducing energy intake by 100 kcal/d by replacing sugar or sugar-containing beverages with noncaloric sweeteners or products containing noncaloric sweeteners, and 2) increasing walking by 2000 steps/d over baseline. After 6 mo, significantly more children in the intervention group than in the control group maintained or decreased their BMI-for-age (Figure 4).
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Fewer studies have been conducted to evaluate the impact of a small-changes approach to reducing energy intake alone on obesity rates. James et al (58) reported initial success in a school-based intervention aimed at reducing the consumption of carbonated soft drinks by children. The percentage of overweight children increased by 7.6% in the control group and decreased by 0.2% in the intervention group. The difference in energy intake due to the intervention was 35–40 kcal/d. However, the impact of the intervention was not sustained over 3 y (59). This illustrates the potential of a relatively modest decrease in energy intake to affect anthropometric variables but also emphasizes the difficulty of sustaining even small behavioral changes.
The available data strongly suggest that excessive weight gain in most of the population is due to a slight degree of positive energy balance and that small lifestyle changes can reduce the energy gap. The small-changes approach has been shown to be effective at increasing total physical activity, decreasing total energy intake, and preventing or reducing excessive weight gain. Given the lack of success with other approaches to lifestyle changes, the small-changes approach deserves serious attention. The small-changes approach might, at a minimum, help prevent things from getting worse until larger societal changes can be made. It remains to be established whether small lifestyle changes are easier to sustain than are larger ones. Although this hypothesis seems reasonable, achieving and sustaining the behavioral change necessary to accomplish this goal, even though only small changes are sought, will take concerted and coordinated efforts across all sectors of society. In effect, the obesity epidemic will only be halted through fundamental lifestyle changes in the way individuals work, play, learn, and socialize.
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CAN THE SMALL-CHANGES APPROACH BE USED TO CHANGE ENVIRONMENTAL DETERMINANTS OF OBESITY? |
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It is a reasonable hypothesis that stopping the obesity epidemic can be approached by reversing the ratchet effect with small, unidirectional changes that would operate to discourage excess weight gain. These changes do not have to be massive, but they need to be in the right direction and they need to be maintained. In effect, this strategy would engage all stakeholders (eg, the policy environment and the commercial environment) to foster a healthy ratchet effect that is always moving in the right direction. This kind of approach has not been tried because there is the tendency to look at the problem as a whole and to consider that no one small change of any kind can cure the problem in its entirety. However, the available data suggest that a small-changes approach may be the fuel needed to move our nation to a new "tipping point," where the conditions change just enough for the population as a whole to embrace even more change than is currently deemed possible.
Adopting the healthy ratchet approach can also be a means to bring together different stakeholder groups that are often difficult to engage because they are so far apart in their immediate goals. Across private and public sectors, virtually every stakeholder is motivated to do something to help prevent obesity. The end goal of the small-changes approach, moving society in a positive direction healthwise, is something that all stakeholders can embrace in a coordinated fashion. Likewise, small changes easily become institutionalized by policy as they are adopted, which would help solve one of the most vexing problems of public health interventions, namely sustainability. In order for something to be sustainable, it has to become "business as usual," moving beyond a "program" or an "initiative" that has only temporary support. It is important to support an approach that makes it hard to slip back into old habits. This strategy has appeal because it does not require stakeholders to abandon their current business or interest wholesale, but empowers them to contribute something positive to the solution.
The ideal way to sustain positive change is to have it become a key driver of the American way of life. If the desired behaviors are in high demand because people are motivated and rewarded, they will have a greater chance of being adopted long term. In a crude sense, to make an impact in today's culture, there needs to be a compelling business model. There has to be a clear benefits exchange between the provider and the consumer, and it has to fit within the current economic and social values structure. For example, a business model for food already exists. An entire industry supplies food to the market, and the particular types of food vary according to consumer demand. So, if one wants to change some elements of the food supply, it is feasible to estimate the demand, the economics, supply chain requirements, etc. In contrast, the business model for physical activity either does not exist or is grossly underdeveloped. Fitness clubs and sports industries sell goods and services that support physical activity, but they are small industries compared with the food industry. Physical activity is not a requirement for survival, so there is no strong biological drive for it. There is no requirement for physical activity as a driver of the economy. No data as yet provide compelling evidence that physical activity improves productivity, reduces health care costs, or improves some other aspect of our lives that is tied to the current economic values system. It is reasonable to hypothesize that it will be difficult to increase physical activity levels on a population level unless there is compelling evidence for making physical activity "worth" something to society as a whole, beyond just enhancing individual health.
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CAN THE SMALL-CHANGES APPROACH SERVE AS THE FOUNDATION FOR A NATIONAL CAMPAIGN TO ADDRESS OBESITY? |
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ACKNOWLEDGMENTS |
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The author's responsibility was as follows: JOH: wrote and reviewed the manuscript. JOH has served on advisory boards for PepsiCo, General Mills, the Wrigley Science Institute, and the McCormick Science Institute.
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REFERENCES |
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This article has been cited by other articles:
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  J. J. Otten, K. E. Jones, B. Littenberg, and J. Harvey-Berino Effects of Television Viewing Reduction on Energy Intake and Expenditure in Overweight and Obese Adults: A Randomized Controlled Trial Arch Intern Med, December 14, 2009; 169(22): 2109 - 2115. [Abstract] [Full Text] [PDF]
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 J. F. Wilson Can Disease Prevention Save Health Reform? Ann Intern Med, July 21, 2009; 151(2): 145 - 148. [Full Text] [PDF]
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ABSTRACT
INTRODUCTION
