Project : USDA ARS

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Research Project: Dietary Guidelines Adherence and Healthy Body Weight Maintenance

Location: Healthy Body Weight Research

2018 Annual Report

Objectives
Objective 1: Identify psychological and physiological processes and factors that influence the motivation to exercise and to eat. Objective 1A. Determine whether incentive sensitization for physical activity is dependent on the dose and the pattern/intensity of physical activity. Objective 1B. Determine whether the level of negative energy balance influences the magnitude of alterations in food reinforcement. Objective 2: Determine whether the relative reinforcing value of vegetables or fruits can be increased through repeated exposure. Objective 3: Determine the effect of meal macronutrient composition on energy metabolism and substrate utilization and satiety. Objective 3A: Compare the effects of high- vs. low-protein breakfasts as components of two patterns of daily protein intake (even distribution of protein across all meals vs. a skewed distribution with most protein consumed at the evening meal) on energy metabolism, substrate oxidation, satiety and the reinforcing value of high-sugar, after-meal snack foods. Objective 3B: Determine the effects of consuming a sugar-sweetened beverage as part of low- (55% CHO, 15% PRO, 30% FAT) or high-protein (40% CHO, 30% PRO, 30% FAT) meals on energy metabolism and substrate oxidation, and satiety and RRV of high-sugar, after-meal snacks.

Approach
Achieving and maintaining healthy body weight underlies many critical aspects of health. The immediate choices people make about their foods and physical activities have cumulative effects that affect body weight and, ultimately, health. Yet, the motivational bases of those choices remain poorly understood; as are ways those choices may be moved towards healthier alternatives. This knowledge is needed for the development of new and effective tools to promote behavioral choices that support healthy body weight. This project addresses these needs by investigating how to increase the reinforcing value of physical activity, and ways to increase the reinforcing value of vegetables and fruits. It also will evaluate the motivating potential of providing real-time feedback on subject energy balance based on an analysis of breath. This project will yield empirical evidence that will inform dietary and physical activity guidelines and programs, and tools that can be used by workers in the health and fitness industries to help individuals make healthy choices regarding physical activity, diet, and maintenance of a healthy body weight.

Progress Report
Objective 1A: Objective 1 is developing an exercise program to increase exercise behavior and maintenance of healthy body weight. The aim is to increase exercise reinforcement, which could shift choice towards exercise and away from less healthy, sedentary alternatives. We have found that a positive outcome expectancy of a treatment is required to develop behavioral tolerance, which further promotes high intensity exercise participation. This project will yield evidence that will inform how to help Americans meet the physical activity guidelines; how to develop exercise programs that are more likely to promote exercise as a habit; and maintenance of health and a healthy body weight. Thirty of 60 subjects have been recruited and have begun or completed the human study. Ancillary studies for Objective 1 include: Completion of a study to understand why some individuals lose more weight with exercise training than others. This study determined whether there are physiological (i.e., hormonal) and behavioral (increases in the motivation to eat, reductions in the motivation to be active, usual physical activity, usual energy intake) mechanisms that explain why some people compensate (respond) to the energy expended during exercise by eating more or being less active throughout the day resulting in no or little weight change. The study found that people expending 600 kcal/day, 5 days per week for 12 weeks in exercise had the same compensation as those expending 300 kcal/day in exercise. Thus, those expending 600 kcal/day lost weight and fat while those expending 300 kcal/day did not lose weight or fat. A second ancillary study for Objective 1 is determining whether playing active videogames increases the attractiveness of physically active play for children. 50 participants are needed; to date all 50 have finished the study and data cleaning and processing are underway. Objective 2: Objective 2 is determining whether repeated exposure to fruits or vegetables can increase the motivation to consume fruits or vegetables. This research is complete with 102 participants completing the 16-week long randomized, controlled study. We found that incentive sensitization, or repeated exposure, to vegetables in the amounts recommended by the Dietary Guidelines for Americans did not result in increased motivation to eat vegetables. This has implications for nutrition researchers, public health workers, and dietitians/nutritionists who work with U.S. consumers to improve diet quality by including vegetables into the diet. Three scientific abstracts have been presented and the results of the primary outcome are in preparation. Objective 2B: The human study protocol was developed, and Institutional Review Board approval obtained. The study will commence human subject recruitment in the fall of 2018. Ancillary studies for Objective 2 include: Determining the dose-response relationship between vegetable intake and skin and blood carotenoid concentrations. If it is found that skin carotenoids are responsive to changes in small amounts of vegetables consumed, skin carotenoid status will be a useful tool for researchers and public health workers to measure compliance with interventions aiming to increase vegetable intake. To date, 32 participants have completed the 8-week study and 19 more have been recruited and are beginning in FY18. It is expected that the full 80 participants will complete the study by the end of calendar year 18. In another ancillary study, samples from one of our previous 28-wk single-arm fruit and vegetable feeding intervention in humans were assayed to determine whether high fruit and vegetable intake is beneficial to bone health. Low intake of fruits and vegetables increased serum bone resorption markers and decreased serum bone formation markers. However, high intake of fruits and vegetables decreased bone resorption markers and increased bone formation markers. These results demonstrate that consumption of fruits and vegetables at or above federal dietary guidance improves bone health. This work was published in British Journal of Nutrition. Objective 3A: Objective 3 is developing a better understanding about the relationship between eating patterns and energy metabolism. We have found that alterations in dietary protein with a sugary or diet drink significantly changes energy metabolism and the reinforcing value of different energy-dense snack foods. We are currently studying the effects of the daily distribution of protein intake on energy metabolism and the reinforcing value of energy-dense snack foods. Eighteen of 40 subjects have been recruited and have begun or completed the human study. Ancillary studies for Objective 3 include: Completion of a study to determine the psychoactive response of consuming chocolate with varying cocoa, fat and sugar concentrations. This study determined which combination of these main components available in commercially prepared chocolates is associated with the greatest reinforcing potential. The study found a measurable psychoactive dose-effect relationship with each incremental increase in the chocolate’s sugar content and decrease in the cocoa and fat content. A second subordinate study for Objective 3 is testing the efficacy of two patterns of daily protein intake (32% from beef) to promote healthy changes in body composition and dietary adherence during weight loss. Fourteen of 46 participants have been recruited and have begun or completed the human study. A third subordinate study for Objective 3 is testing the degree of caloric restriction required to detect a noticeable shift the in the ratio of carbon 13 to carbon 12 in breath. The carbon signature of our breath reflects the foods we eat and the fuel source (fat or carbohydrate) our body is using. Different plants use the carbon in the atmosphere differently and with modern technology, we can detect these differences. Because we are what we eat, these differences in what is called the isotopic signature are reflected within our body. In the body, fat discriminates against the heavier carbon 13, incorporating primarily the lighter carbon 12. When the body switches to using fat as fuel it is reflected in the breath changes. We are able to take advantage of these processes to determine how quickly the body switches to burning fat when calories are restricted and how the foods we eat can disrupt this measurement. All participants have been recruited and have completed the human study. We are playing important roles in the development of the ARS Beef Grand Challenge team. We are an integral part of the planning team, having participated in planning meetings since the early idea formation of a Beef Grand Challenge initiative.

Accomplishments
1. Exercise may aid in weight loss, provided you do enough. Demonstrated why some people lose weight with exercise and some do not. One reason that exercise may not be highly motivating to people is that it does not produce the amount of weight loss that they expected it would. ARS researchers in Grand Forks, North Dakota demonstrated why some individuals lose more weight with exercise training than others. This study demonstrated that people who expended 600 kcal/day, 5 days per week for 12 weeks in exercise ate the same number of additional calories as those people who expending 300 kcal/day in exercise. Thus, those expending 600 kcal/day lost weight and fat while those expending 300 kcal/day did not lose weight or fat. This work shows that people can lose weight and fat with exercise, but that they have to expend more than 1500 calories/week and probably closer to 3000 calories/week exercising to have meaningful changes in weight.

2. Exercise - do it until you like it. Demonstrated that the motivating value of exercise can be increased. Most Americans do not participate in enough physical activity to meet the physical activity guidelines and therefore do not receive all the health benefits of engaging in physical activity. ARS researchers in Grand Forks, North Dakota demonstrated, for the first time, that aerobic exercise training for 6 weeks increased the motivating value of exercise in some adults. Increasing the motivating value of exercise should help people to develop exercise as a habit and help them to them to meet the physical activity goals detailed in the Dietary Guidelines for Americans.

3. More evidence that Americans have a hard time incorporating vegetables into their daily diet. Demonstrated that repeated exposure to vegetables does not increase people’s motivation to eat vegetables. Very few Americans meet the Dietary Guidelines for Americans’ recommendations for vegetable intake. ARS researchers in Grand Forks, North Dakota provided recommended amounts of vegetables to overweight and obese individuals for 8 weeks and measured their motivation before and after consuming the vegetables. Although compliance was very high, our findings show that it is very difficult to increase vegetable intake in overweight and obese individuals. This work has implications for future dietary interventions in Americans to increase vegetable intake to recommended amounts.

4. Psychoactive reasons for American’s love of milk chocolate. Demonstrated the psychoactive effect of consuming chocolate varying in cocoa, sugar and fat concentrations in a dose dependent manner using a validated Addiction Research Center Inventory “drug effects” questionnaire. The questions used simultaneously reflect alterations in motivation, mood, sensation and perception, and therefore, provide insight into the interrelation of these variables and chocolate consumption. ARS researchers in Grand Forks, North Dakota demonstrated, for the first time, a measurable psychoactive dose-effect relationship with each incremental increase the chocolate’s sugar content and decrease in the cocoa and fat content. Overall, there is an inverse dose-effect relationship with cocoa concentration and a positive dose-effect relationship with the sugar content of a chocolate. This research helps to explain the links between brain and sugar intake, and why it is so difficult for Americans to decrease sugar consumption. Understanding these links may help improve Americans’ diets.

5. A diet high in carotenoid-rich foods favorably impacts chronic-low-grade inflammation. Systemic inflammation is a hallmark of many chronic diseases, and studies have suggested that high intakes of vegetables and fruits may favorably impact inflammatory markers. ARS researchers in Grand Forks, North Dakota completed a controlled-feeding trial with ~6 cups of fruits and vegetables per day and found that, among already healthy individuals, some beneficial inflammatory markers increased while other detrimental markers decreased. These results are important as they demonstrate beneficial effects of consuming more fruits and vegetables, and can be used by the scientific community and consumers to guide fruit and vegetable serving amounts to decrease chronic disease risk.

6. Eggs are for dinner too! Diet quality among low-income individuals remains low, and little research has examined how making small dietary changes can affect nutrient intake. Eggs are a nutrient-dense, low-cost food group that is usually only consumed at breakfast. ARS researchers in Grand Forks, North Dakota demonstrated that consuming eggs for dinner or lunch did not change total nutrient intake but decreased the prevalence of inadequate vitamin D. However, substituting eggs for cereal at breakfast increased the prevalence of folate inadequacy. These results have implications for consumers and for clinicians and public health workers who advise low-income individuals on increasing diet quality while keeping food costs lower.

7. Recognition of Federal dietary guidance icons is associated with greater diet quality. Federal dietary guidance takes the form of social media, websites and printed materials for the purpose of improving the diets of Americans. ARS researchers in Grand Forks, North Dakota used a large, nationally-representative dataset to examine whether knowledge of the icons, such as My Plate, were associated with diet quality. Scientists demonstrated that Americans who reported having heard of the icons had greater compliance with the Dietary Guidelines for Americans, indicating that federal dietary guidance does work. Scientists also determined that many low-income individuals had not heard of the icons. This information is crucial for public health workers and policymakers in guiding education efforts to follow the Dietary Guidelines for Americans.

U.S. DEPARTMENT OF AGRICULTURE

Healthy Body Weight Research: Grand Forks, ND