# Presentation: 035517

## Can eating fruits and vegetables help people to manage their weight?

**Notes:**
This PowerPoint presentation is based on the Research to Practice Series, No. 1: Can eating fruits and vegetables help people to manage weight? (January 2005)  This series is developed by the Division of Nutrition and Physical Activity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention.

## There are many proposed strategies for losing or maintaining weight.

- This presentation looks at only one strategy:
- 	Substituting low-energy-dense fruits and vegetables for foods with high energy density to lower calories.

**Notes:**
There are many weight loss strategies that have been proposed over time—some valid, some not.  This presentation is not designed to take all these strategies into account.  It is only meant to look at one strategy, which is substituting low-energy-dense fruits and vegetables for foods with high energy density and calories.

## What Is Energy Density?

- The relationship of calories to weight of food (calories per gram).
***High-energy-dense foods***: 4-9 cal per gram
- 	(cookies, crackers, butter, bacon)
***Medium-energy-dense foods***: 1.5-4 cal per gram (bagels, dried fruits, hummus, part-skim mozzarella)
***Low-energy-dense foods***: 0-1.5 cal per gram
- 	(most fresh fruits and vegetables, fat-free yogurt, broth-based soups)

**Notes:**
Energy density is key to understanding why fruits and vegetables can be helpful in a weight management program.  Energy density is simply the number of calories in food relative to its weight.  Foods with high calories in relation to their weight, such as fats and oils, are high-energy-dense foods. Medium-energy-dense foods have fewer number of calories per gram of weight. These are foods like bagels, hummus, dried fruits and low fat cheese.  And finally, foods with very few calories in relation to their weight, such as fresh fruits and vegetables, are low-energy-dense foods.

There are many foods in these categories.  These are only a few examples.  In this presentation we will focus primarily on fruits and vegetables when we talk about the low-energy-dense category.

## Dietary Guidelines for Americans (2005)

- “...calorie-lowering strategies include eating foods that are low in calories for a given measure of food (e.g., many kinds of vegetables and fruits and some soups).
- ...make substitutions to avoid excessive calorie intake.”

**Notes:**
The Dietary Guidelines for Americans recommends substituting low-energy-dense foods like fruits and vegetables for high-energy-dense foods to lower the number of calories one eats to help manage weight.

The research in this presentation will support this recommendation.

## This presentation will show:

- Feeling full is one reason people stop eating.
- Volume affects the feeling of being full.
- Low-energy-dense foods have fewer calories than the same volume of high-energy-dense foods. People who eat low-energy-dense foods can feel full while eating fewer calories.
- Water and fiber increase volume and reduce energy density.
-  Fruits and vegetables have high water and fiber content and are low in calories and energy density.
**Conclusion: Fruits and vegetables are good substitutes for high-energy-dense foods in a weight management program. **

**Notes:**
The studies that we will review provide the logical framework that leads to associating eating fruits and vegetables as a weight management strategy.

## So how do people lose weight?

- To lose weight people must consume fewer calories than they expend.
- The amount or volume of food a person eats prompts a feeling of being full.
- Feeling full is one reason that people stop eating.

## Studies show that feeling full is likely to make a person stop eating—even more than the total calories in the food.

- 20 participants ate as much as they wanted from food offered to them over 5 days.
- Diet alternated from low-energy-dense to high-energy-dense foods.
- On the low-energy-density diet, the participants felt full with just over half the calories (1570 kcal) they needed to feel full on the high-energy-density diet (3000 kcal).

**Notes:**
Many people believe that consuming high-calorie foods will make them feel full.  However, a study by Duncan and colleagues had a different outcome.  20 obese and nonobese participants ate as much as they wanted over 5 days from food offered to them.  The diet alternated from low-energy-dense foods, which is low-calorie, high-volume food, to high-energy-dense foods (high-calorie, low-volume).
(Results on slide)

Duncan KH, Bacon JA, Weinsier RL. The effects of high and low energy density diets on satiety, energy intake, and eating time of obese and nonobese subjects.  Am J Clin Nutr 1983;37:763-7.

## Eating Low-Energy-Dense Foods = Fewer Calories Consumed and Equal Feelings of Being Full

- Researchers gave meals and snacks for 2 days to women who were assigned to a low-, medium-, or high-calorie menu.The women in each group ate until full.
- All groups ate a similar amount or volume of food.
- Study suggests that volume of food, not calories, makes people feel full.

**Notes:**
In this study, 3 groups of women were provided meals and an evening snack for 2 days.  One group followed a low-calorie menu; the second, a medium-calorie menu; and the third, high-calorie menu.  The 3 menus were similar except that more vegetables were offered in the medium- and low-calorie menus to reduce their overall caloric content. 

The researchers found that women in each group ate a similar amount of food, which resulted in the medium-calorie group consuming more calories than the low-calorie group and the high-calorie group consuming more than either of the other 2 groups.

Bell EA, Castellanos VH, Pelkman CL, Thorwart ML, Rolls BJ. Energy density of foods affects energy intake in normal-weight women.  Am J Clin Nutr 1998;67:412-20.

## Volume affects energy density and the feeling of being full.

- Yogurt shakes 30 minutes before lunch on 3 different days.
- Three sizes: 300 ml, 450 ml, and 600 ml, BUT had equal calories. (Higher volume achieved by incorporating air.)
- Calories consumed at lunch were 12% lower following consumption of 600 ml milkshake.
- Participants reported greater feelings of fullness after drinking the 450 ml milkshake or the 600 ml milkshake than after the 300 ml drink.

**Notes:**
Although we will primarily focus on fruits and vegetables, we have included this study to show how foods can be altered to lower their energy density and increase their volume.  In this study, researchers created a greater volume of yogurt shakes simply by adding air.  Volume in this presentation means the same as amount.  It refers to the space occupied by something rather than its weight.

Researchers had  28 men eat 3 meals in the laboratory 1 day a week for 4 weeks.  On 3 of the 4 days the participants were given a yogurt-based milkshake 30 minutes before lunch.  The milkshakes varied in volume (300 ml, 450 ml, and 600 ml) and were equal in caloric content because the higher volume was achieved by incorporating air.
All three “sizes” had identical ingredients and weighed the same.  

The participants consumed 12% fewer calories after drinking the 600 ml milkshake, and they reported greater increases in feelings of fullness after drinking the 450 ml milkshake or the 600 ml milkshake than after the 300 ml drink.  

Rolls BJ, Bell EA, Waugh BA.  Increasing the volume of a food by incorporating air affects satiety in men.  Am J Clin Nutr 2000;72:361-8.

## Water, Energy Density, and Feeling of Being Full

- 24 women ate the same foods, but prepared differently over 3 days:
- Day 1: chicken-rice casserole (1 1/3 cups).
- Day 2: chicken-rice casserole with a glass of water.
- Day 3: chicken-rice soup (21⁄2 cups). Soup was made by adding the water into the casserole ingredients used the day before.
***Eating the soup***
- 	- significantly increased the feeling of fullness
- 	- reduced the participants’ hunger
- 	- significantly reduced the number of calories the women consumed during lunch.

**Notes:**
Adding water to foods is another way to lower energy density and increase volume.

In this study, twenty-four women ate breakfast, lunch, and dinner in the laboratory 1 day a week for 4 weeks.  On 3 days of the 4 days, they were served a dish made of the same ingredients but prepared differently.  

On 1 day, they were served a chicken-rice casserole; the second, a chicken-rice casserole with a glass of water; on the third chicken-rice soup. The soup was made by adding the water into the casserole ingredients used the day before.  Serving size was 1 1/3 cups for the casserole and 2 1⁄2 cups for the soup.  

Eating the soup significantly increased the feeling of fullness and reduced the participants’ hunger, also significantly reducing the number of calories the women consumed during lunch.  Drinking a glass of water with the casserole had no effect on total calories consumed or on feelings of being full.

Rolls BJ, Bell EA, Thorwart ML.  Water incorporated into a food but not served with a food decreases energy intake in lean women.  Am J Clin Nutr 1999;70:448-55.  

## A literature review found similar findings:

- Short-term studies: low-energy-dense foods promoted feeling full, reduced hunger, and eating fewer calories.
- Long-term studies: low-energy-dense foods promoted moderate weight loss.
- Studies lasting longer than 6 months: weight loss 3 times greater in people who ate foods of low energy density than in those who simply ate low-fat foods.

**Notes:**
Other studies have yielded similar findings.  In a literature review by Yao and Roberts in 2001, the authors found in short-term studies that eating low-energy-dense foods promoted feelings of being full, reduced hunger, and eating fewer calories regardless of how the food was changed to lower the energy density (such as reducing fat).  

 In the long-term studies they reviewed, eating low-energy-dense foods promoted moderate weight loss.  In studies lasting longer than 6 months, weight loss was 3 times greater in persons who ate foods of low energy density (low in fat and high in fiber) than in those who simply ate low-fat foods.  

This study looked at low-energy-dense foods, not just fruits and vegetables.

Yao M, Roberts SB. Dietary energy density and weight regulation. Nutr Rev 2001;59:247-58.

## Fruits and Vegetables = Low Energy Density

- Fat increases the energy density of foods.
- Water and fiber in foods increase volume and reduce energy density.
- In their natural state, fruits and vegetables have high water and fiber content and are low in fat and energy density.
- The USDA’s Web site on food composition (_[www.](http://www.nal.usda.gov/fnic/foodcomp)__[nal](http://www.nal.usda.gov/fnic/foodcomp)__[.](http://www.nal.usda.gov/fnic/foodcomp)__[usda](http://www.nal.usda.gov/fnic/foodcomp)__[.](http://www.nal.usda.gov/fnic/foodcomp)__[gov](http://www.nal.usda.gov/fnic/foodcomp)__[/](http://www.nal.usda.gov/fnic/foodcomp)__[fnic](http://www.nal.usda.gov/fnic/foodcomp)__[/](http://www.nal.usda.gov/fnic/foodcomp)__[foodcomp](http://www.nal.usda.gov/fnic/foodcomp)_) lists the water, fiber content, and many other food components including calories for hundreds of vegetables and fruits.

**Notes:**
Water, which has no calories, and fiber in foods increase the volume and reduce energy density.  We saw this in both the yogurt shake and the casserole/soup studies.  When water was introduced, the resulting product was larger, but had no more calories.  When there is the same number of calories, but larger size or weight, energy density is lower.  

In their natural state, that is, not covered with rich sauces, fried, or baked in a pie or other dessert, fruits and vegetables have high water and fiber content and are low in fat and therefore low in energy density.   

Although there are a number of foods that are low in energy density that can be substituted for high-energy-dense foods, fruits and vegetables are a good choice because of all the nutrients they provide for good health and preventing some chronic diseases.

## Studies with fruit and fruit juices show:

- Whole fruit is more satiating.
- Whole fruit contains fiber, and juice is fiber-free.

**Notes:**
Some researchers have studied the effects of water and fiber in foods by conducting their studies on different forms of fruits, for example, whole, puree, and juice.  A study that compared whole apples with puree and juice found that whole apples with 2.9% fiber had higher satiety ratings than puree or fiber-free apple juice.  The authors attributed the differences in satiety to the fiber content of the foods and its effect on glucose homeostasis.  

Another study that compared whole oranges with 2.5% fiber to orange juice, which is fiber free, and whole grapes with 1.3% fiber to grape juice which is fiber free confirmed that whole fruit provided more satiety than juice. Instead of one serving of orange juice which is 6 ounces and 85 calories, a person can eat a medium orange and consume only 65 calories and obtain much more fiber and volume.

Therefore, the physical form of food impacts feelings of fullness.

Haber GB, Heaton KW, Murphy D, Burroughs LF.  Depletion and disruption of dietary fibre.  Effects on satiety, plasma-glucose, and serum insulin.  Lancet 1977;2:679-8
Bolton RP, Heaton KW, Burroughs LF.  The role of dietary fiber in satiety, glucose, and insulin: studies with fruit and fruit juice.  Am J Clin Nutr 1981;34:211-17.

## Vegetables, Fiber, Water and Feeling Full

- Researchers found that adding vegetables (carrots and spinach) to meals with equal calories enhanced the feeling of being full if at least 200 g of vegetables were added.
- Ratings of fullness were correlated positively with the fiber content, water content, and the total weight of the meal.

**Notes:**
In studies that tested the influence of vegetables on feeling full, a group of researchers found that adding vegetables (carrots and spinach) to meals with equal calories enhanced the feelings of being full if at least 200g of vegetable were added.  

These studies did not distinguish whether the effect was related to the vegetables’ fiber and water content or the reduction of energy density of the food. However, the ratings of fullness were correlated positively with the dietary fiber content, the water content, and the total weight of the meal.  

Gustafsson K, Asp N-G, Hagander B, Nyman M.  Effects of different vegetables in mixed meals on glucose homeostasis and satiety.  Eur J Clin Nutr 1993;47:192-200.
Gustafsson K, Asp N-G, Hagander B, Nyman M. Dose-response effects of boiled carrots and effects of carrots in lactic acid in mixed meals on glycaemic response and satiety.  Eur J Clin Nutr 1994;48:386-96.
Gustafsson K, Asp N-G, Hagander B, Nyman M. Satiety effects of spinach in mixed meals: comparison with other vegetables.  Int J Food Sci Nutr 1995:46:327-34.
Gustafsson K, Asp N-G, Hagander B, et al.  Influence of processing and cooking of carrots in mixed meals on satiety, glucose and hormonal response.  In J Food Sci Nutr 1995;46:3-12.

## Dietary Fiber and Weight Management

- In a review of 22 studies, 20 studies found that high-fiber diets resulted in weight loss.
- Even in studies that did not restrict food intake, those on higher-fiber diets lost significantly more weight than those on the lower-fiber diets.
- An increase of 14g of fiber a day was associated with an average weight loss of over 4 lb. in nearly 4 months.

**Notes:**
Dietary fiber, regardless of the source, has also been linked to weight regulation. A review summarizing the effects of high- versus low- fiber diet interventions found that the high fiber diets in 20 of 22 studies resulted in weight loss. 

Using pooled data from 12 of the intervention studies that did not control energy intake, the authors found that the participants on the higher-fiber diets lost significantly more weight than those on the lower-fiber diets.  From those same studies it was found that an increase of 14 g of fiber a day was associated with an average weight loss of over 4.2 lb in nearly 4 months. 

These analyses highlight the importance of fiber-rich foods, such as fruit and vegetables, in weight regulation.  

Howarth NC, Saltzman E, Roberts SB.  Dietary fiber and weight regulation.  Energy density of foods affects energy intake across multiple levels of fat content in lean and obese women.  Am J Clin Nutr 2001;73:1010-18.

## Review of Dietary Interventions

- Many studies found that significant weight loss can occur when advice to increase the intake of fruits and vegetables is coupled with advice to reduce energy intake.

**Notes:**
Although no studies have directly linked consumption of fruits and vegetables to weight loss, many studies have considered fruit and vegetable consumption in the management of chronic diseases while also reporting on weight loss and maintenance. Many of these studies are included in a recent comprehensive review of intervention studies. 

The review’s authors concluded that significant weight loss can occur when advice to increase intake of fruits and vegetables is coupled with advice to reduce energy intake.  Some of the studies reviewed are highlighted in the following slides. 

Rolls BJ, Ello-Martin JA, Tohill BC.  What can intervention studies tell us about the relationship between fruit and vegetable consumption and weight management?  Nutr Reviews 2004;62:1-17.

## Intervention 1: MRFITMultiple Risk Factor Intervention Trial

- Participants advised to reduce fat and increase fruit and vegetable consumption and whole grains to lose weight and improve blood lipids and blood pressure.
- Increases in fruit and vegetable intake were related to maintenance of weight loss.
- Participants who lost more weight ate more fruits and vegetables than the others.
- 					***Dietary Intervention Review***

**Notes:**
In the Multiple Risk Factor Intervention Trial (MRFIT), the participants were counseled to reduce fat and increase fruit and vegetable consumption to help lose weight and improve blood lipids and blood pressure. 

The recommendations emphasized fat reduction to less than 35% of energy from fat, increased intake of fruits and vegetables to 5 or more servings per day, and an increased consumption of grains. 

An increase in fruit and vegetable intake was related to maintenance of weight loss, and participants who lost more weight also showed a greater intake of fruits and vegetables. Participants made significant increases in their intakes of grains, fruits, and vegetables and decreased fat, all of which made an important contribution to weight loss. 

Dolecek TA, Stamler J, Caggiula AW, et al.  Methods of dietary and nutritional assessment and intervention and other methods in the Multiple Risk Factor Intervention Trial.  Am J Clin Nutr 1997;65(suppl 1):196S-201S.

## Intervention 2: Reduced Calories, Low Fat, High Complex Carbohydrates

- Unlimited fruits and vegetables for 6 months.
- 147 (69%) of the participants lost weight (average: 14 lb.)
- Over 25 months follow-up—
- 	- 53% continued to lose or maintain their weight.
- 	- mean net weight loss from pretreatment to end of
- 		follow-	up: over 17 lb.
- 					 ***Dietary Intervention Review***

**Notes:**
In this study 213 obese adults were encouraged to change their eating habits to an energy-restricted diet of low-fat, high-complex-carbohydrate foods emphasizing unlimited fruits and vegetables. 

Over the time period of the study, 147 (69%) of the participants were successful at losing weight, with the average loss of almost 14 lb. 

Over an average of 25 months of follow-up (range 4 to 76 months), 53% of participants continued to lose or maintain their weight, and the mean net weight loss from the pretreatment to end of follow-up was over 17 lb. 

Fitzwater SL, Weinsier RL, Wooldridge NH, et al. Evaluation of long-term weight changes after a multidisciplinary weight control program. J Am Diet Assoc 1991;91:421-4.

## Intervention 3: Families with Obese Parents, Nonobese Child

- Parent-focused behavioral intervention.
- Two groups: Both had a comprehensive behavioral program.
- 		- One group increased fruit and vegetable consumption.
- 		- Second group decreased high-fat and high-sugar foods.
- Materials for the children targeted the same dietary changes as for their parents, but with no calorie restrictions.
- After 1 year—
- 	- Parents in fruit and vegetable group greater decreases in weight than 	the parents in the decreased fat and sugar group.
- 	- Parents and children in the increased fruit and vegetable group also 	decreased consumption of high-fat and high-sugar foods.
- 					***Dietary Intervention Review***

**Notes:**
In a study published in 2001, researchers evaluated the effect of a parent-focused behavioral intervention on the eating habits of parents and children in families that had at least one obese parent and a nonobese child.  

The families were randomized to two groups.  Parents in both groups were given a comprehensive behavioral weight-control program, but one group was encouraged to increase fruit and vegetable consumption, while the second group was urged to decrease the amount of high-fat and high-sugar foods.  

Materials for the children targeted the same dietary changes as for their parents, but with no calorie restrictions.  

After 1 year, parents in the fruit and vegetable group had significantly greater decreases in weight than the parents in the decreased fat and sugar group.  Furthermore, the parents and children in the increased fruit and vegetable group had decreased their consumption of high-fat and high-sugar foods. 

Epstein LH, Gordy CC, Raynor HA, Beddome M, Kilanowski CK, Paluch R.  Increasing fruit and vegetable intake and decreasing fat and sugar intake in families at risk for childhood obesity.  Obesity Res 2001;9(3):171-8.

## Intervention 4: Increased Fruits and Vegetables, Decreased Fat

- Participants consumed a daily diet with specific amounts of fruit, vegetables, juice plus fiber, 15-20% fat.
- After one year:
- Energy-adjusted intake of vegetables and dietary fiber, but not fruit, associated with a decrease in BMI.
- Decrease in percent energy from fat not associated with a drop in BMI.
- 			***Dietary Intervention Review***

**Notes:**
A few intervention trials have included advice to increase consumption of fruits and vegetables with advice to reduce fat intake without having a specific weight loss component in the intervention.  

In this study participants were counseled to consume a daily diet that included specific amounts of fruit, vegetable, and juice servings, as well as fiber, and had 15 to 20% of energy from fat.  

After 1 year, the intervention and control groups did not differ significantly in body mass index.  Combined data from the 2 groups indicated that 11% lost weight, 74% maintained weight, and 15% gained weight.  

Analysis of the diets of the participants who lost weight showed that increases in energy-adjusted intakes of vegetables and dietary fiber but not fruit were associated with a decrease in BMI.  A decrease in percent energy from fat was not, however, associated with a drop in BMI. 

Rock CL, Thomson C, Caan BJ, et al.  Reduction in fat intake is not associated with weight loss in most women after breast cancer diagnosis: evidence from a randomized controlled trial.  Cancer 2001;91:25-34.

## Intervention 5: Polyp Prevention Trial

- Participants increased intake of fruits and vegetables and decreased fat—
-   Lost significant amount of weight in one year.
***	******	******	******	******	******Dietary Intervention Review***

**Notes:**
One analysis of the Polyp Prevention Trial reported that participants significantly increased their intake of fruits and vegetables and decreased their intake of fat within the first year of the study, losing a significant amount of weight. Again, however, the intervention did not have a specific weight loss component. 

Lanza E. Schatzkin A, Daston C, et al.  Implementation of a 4-y, high-fiber, high-fruit-and-vegetable, low-fat dietary intervention: results of dietary changes in the Polyp Prevention Trial.  Am J Clin Nutr 2001;74:387-401.

## Intervention 6: Cardiac Trials: Lower Fat and Increased Fruits and Vegetables

- In a series of trials, cardiac patients who changed their diets by lowering fat intake and increasing fruits and vegetables lost a significant amount of weight.
- 					***Dietary Intervention Review***

**Notes:**
Finally, in a series of trials, cardiac patients who were encouraged to change their diets by lowering fat intake and increasing fruits and vegetables lost a significant amount of weight during follow-up. 

In summary, these studies that focused on chronic disease outcomes and gave combined advice to increase fruits and vegetables and decrease dietary fat without explicitly advising weight loss often found participants either maintaining their body weight or spontaneously losing weight during follow-up. 

Singh RB, Rastogi S, Verma R, et al. Randomised controlled trial of cardioprotective diet in patients with recent acute myocardial infarction: results of a one year follow up.  Br Med J 1992;304:1015-9.
Singh RB, Rastogi S, Niaz MA, et al.  Effect of fat-modified and fruit- and vegetable-enriched diets on blood lipids in the Indian Diet Heart Study.  Am J Cardiol 1992;70:869-74.
Singh RB, Dubnov G, Niaz MA, et al.  Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): a randomized single-blind trial.  Lancet 2002;360:1455-61.

## Conclusion

- Feeling full cues people to stop eating.
- People feel full based on the volume of food consumed, not necessarily number of calories.
- Eating low-energy-dense foods can help people feel full with fewer calories.
- Substituting low-energy-dense fruits and vegetables can be effective in weight loss or maintenance.

## Tips for Eating Fruits and Vegetables in a Weight Management Program:

- Fruits and vegetables should be substituted for foods high in energy density.

## Tips for Eating Fruits and Vegetables in a Weight Management Program:

- To lower the energy density of foods, such as soups, sandwiches, and casseroles, substitute fruits and vegetables for some of the ingredients that have higher energy density, such as high-fat meat, cheese, and pasta.

## Tips for Eating Fruits and Vegetables in a Weight Management Program:

- Breading and frying fruits and vegetables or adding high-fat dressings and sauces greatly increase the calorie and fat content of the dish. Fruits and vegetables in desserts also have high calories, fat, and sugar.

## Tips for Eating Fruits and Vegetables in a Weight Management Program:

- Eat whole fruit instead of juice.
- Frozen and canned fruits and vegetables are good options when fresh produce is not available.  Choose those without added sugar, syrup, cream sauces, or salt.

## Tips for Eating Fruits and Vegetables in a Weight Management Program:

- Vegetables tend to be lower in calories than fruit. Substituting more vegetables than fruit for foods of higher energy density can be helpful in a weight management plan.

## Research Review

- Very few studies on direct relationship between eating fruits and vegetables and losing weight.
- Some studies had few participants.
- Many studies focused on fruit and vegetables in the context of treating high blood pressure or cardiac disease—but reported on weight loss also.
- Some studies examined the short-term impact of eating fruits and vegetables on energy intake.

**Notes:**
Many of the studies in this review are studies done with small numbers of people or were not designed primarily to show that eating fruits and vegetables results in weight loss.  A number of these studies focused on the prevention or treatment of high blood pressure or cardiac disease, but they reported on weight loss also.  Some studies focus on the short-term impact of eating fruits and vegetables on calorie intake at the next meal, but many focus simply on the one eating occasion.