Rolls, PhD, discusses the role of energy density in weight control
Density and Nutrition in Weight Control Management
an evidence-based report of the National Heart, Lung and Blood Institute1
concluded that low-fat diets are associated with spontaneous reduction
of energy intake and body weight. The report further stated that reducing
caloric intake confers additional benefits. The key question I consider
in this presentation is: How do people who are trying to reduce their
caloric intake avoid hunger and feel satisfied?
Here is Where
Diet Composition Becomes Important
diets are associated with weight loss because they have low energy density,
defined as number of calories per portion. At an energy density of 9 kcal/g,
fat has more than twice the number of the calories that carbohydrates
or protein (each with 4 kcal/g) have.2,3 In general, my colleagues
and I have found that among foods most commonly consumed in the United
States, the higher the fat content, the higher the energy density.4
However, an even stronger relation exists between water content and energy
density: The higher the water content of a food, the lower its energy
density4 (Table 1). Water adds weight and volume to foods without
adding calories. Water-rich foods provide bigger, more satisfying portions
than do dry foods. For example, a 100-calorie portion of grapes is eight
times larger by weight than 100 calories of raisins (Figure 1).
density of foods influences hunger, satiety, and food intake. My colleagues
and I have studied how adding water to food (ie, decreasing energy density)
affects satiety. One study5 compared the effect of each of
three first courses--a vegetable-and-rice casserole, the same casserole
served alongside a ten-ounce glass of water, and a soup made by cooking
the water and casserole together--on the quantity of lunch eaten a few
minutes later. Compared with intake of the casserole alone, water consumed
as a beverage with the casserole provided no additional reduction in lunch
intake, whereas incorporating water into the casserole (to make soup)
resulted in a 100-calorie reduction in later intake.5
of possible explanations may account for the effect of energy density
on satiety. In studies using direct intragastric infusion, my colleagues
and I found that people are sensitive to the volume of stomach contents.6
Some of the effect is cognitive and relates to portion size; some of the
effect relates to the sensory stimulation provided by a bigger portion.
show that energy density--not fat content of foods--affects satiety and
food intake. Studies showed also that subjects tended to eat a constant
volume of food and that reduced energy density was associated with spontaneous
decrease in daily energy intake without increased hunger.9,10
consumers use information about energy density to manage their weight,
Robert Barnett and I wrote a book, The Volumetrics Weight-Control Plan,2,3
in which foods are divided into four categories according to their energy
category consists of foods with very low energy density, ie, foods containing
between 0.0 and 0.6 kcal/g. We encourage people to eat as much as they
wish of these foods, which include soups, fruits, and vegetables.
1. Water rich grapes provide bigger, more satisfying portions of
less-energy-dense food than do dried raisins.
category includes most foods that we eat daily: starchy fruits and vegetables,
beans, and lean meat. Under the volumetrics concept, people may continue
to consume relatively large portions of these foods. The energy density
for this category is between 0.6 and 1.5 kcal/g.
density of foods in the third category ranges from 1.5 to 4.0 kcal/g and
includes a wide variety of foods, such as cheese, salad dressings, some
snack foods, and desserts. Intake of these foods, particularly those with
higher energy density, should be moderated.
density of foods in the fourth category ranges from 4.0 to 9.0 kcal/g.
These foods have the highest energy density and include chocolates, fatty
foods (eg, nuts, chips, and other deep-fried foods), and candy. Intake
of these foods requires careful portion control.
approach does not reinvent nutrition; the approach simply follows recommended
dietary guidelines and leads to healthy food choices. Consuming an adequate
balance of nutrients is particularly important for people who eat fewer
calories, because these people are at greater risk for nutritional deficiency.
What's new here is the advice to be more cautious about low-moisture-content
foods, such as pretzels and crackers.
clinical trials using energy density to guide food choices are underway.
Don Hensrud at the Mayo Clinic--the editor of a book on the subject11--has
had success using energy density in a clinical trial. Michael Lowe and
colleagues at Drexel University studied energy density in the weight maintenance
phase of a weight-loss trial12 and found that using energy
density yielded better results than did traditional types of behavior
therapy. My colleagues and I are also doing a clinical trial at The Pennsylvania
need action to combat obesity. The bad news is that the eating environment
is at least partially driving the obesity epidemic; the good news is that
the eating environment can be changed. We must give the food industry
reasons to provide foods that promote satiety: lower-energy-density, good-tasting
foods that don't cost more than less-healthy choices. Although consumers
are responsible for what they put into their mouths, we can make it easier
for them to make reasonable choices.
the presentation, Dr Rolls answered questions from the audience:
industry is showing signs of improvement. For instance, McDonald's®
decided to reduce the amount of trans fat contained in foods that the
company produces. Pepsico® also recently announced plans
to reduce the fat content of snack products by 25% and to eliminate use
of trans fat. Marketing data clearly show that public preferences are
moving in this direction; we must support parallel movement in the food
industry. How can this message--that the energy density of foods must
be decreased--be translated into action by the food industry?
about reducing energy density has two parts 1) Fat still counts, so
reduce it--but not so much that you don't enjoy food; 2) Increase the
water content of your food, primarily by adding fruits and vegetables.
energy density stated on food labels would be good. Even without this
information, though, people can quickly assess energy density: If the
number of calories per serving stated on the Nutrition Facts label is
lower than the number of grams, the food has low energy density. When
the number of calories is close to twice the number of grams (or higher),
the food is in an energy density category that requires the consumer
to be more cautious about portion size. Beyond that, people know what
highly energy-dense foods are: high-fat, low-water-content (ie, dry)
trials, how were subjects taught to do this calculation? Can this idea
be translated into clinical practice?
Lowe used my book, Volumetrics, which is also being used in some
National Institutes of Health (NIH) clinical trials and in the Pennsylvania
public school system. The messages in Volumetrics could
certainly be made more visual. For instance, you could have interactive
computer programs where you could change portion sizes as energy density
varies. My book could be made more fun with pictures, more examples,
and simpler recipes--the book could be made very appealing to consumers.
I'd love someone to develop a brochure based on the concepts discussed
in the book.
comment on the difficulty people have reading nutrition labels and on
how we might be able to get the food industry to give consumers better
industry worked hard to introduce a standard label that contained a
satisfactory amount of information; when you suggest yet another number
to include, they're a little horrified. However, I think a simple number
that people could understand more readily--a number stated in terms
of energy density and portion size--would be great.
one concern is that once people understand energy density, they will
simply eat more if they know they are eating foods that have lower energy
density. We therefore studied the effect of adding information about
energy density on the label and found that in a group of people who
were trained about energy density, labels didn't affect eating behavior.
At least, we found this result in a laboratory-based study.13
believe in daily consumption of five smaller meals (ie, consisting of
250 to 300 calories each) instead of three larger meals a day? And do
you think the protein recommendation (15% of daily caloric intake) is
of eating is a difficult area of research. The evidence about whether
frequency affects metabolism and body weight is controversial.
justifiably say that one pattern will work for everybody. Part of the
challenge is to identify meal patterns and types of foods that people
can live with.
and human studies indicate that of the macronutrients, protein has the
most satiety value.14,15 But has any really good study been
done on protein and satiety? I don't think so; we clearly need to do
more work. Protein comes with fat, too, and epidemiologic data indicate
that, in general, people who eat more protein are heavier.
is that consumption of fruits and vegetables will be inadequately emphasized
if we focus only on labeling. How do we keep fruits
and vegetables in view?
we want to tell people that they can, in general, eat unlimited amounts
of fruits and vegetables. The minimum five-a-day-fruit-and-vegetable
message is very valid. Under the auspices of the Produce for Better
Health Foundation and the Centers for Disease Control and Prevention
(CDC), we are working on a review of the effect of fruits and vegetables
on weight management.
problems with fruits and vegetables exist: Produce is often of poor
quality, unavailable, or simply not consumed. Therefore, although the
government's job is not necessarily to increase public consumption of
fruits and vegetables or to make them more affordable, the US Department
of Agriculture (USDA) is actively rethinking the food stamp and Women,
Infants and Children (WIC) programs as a way to increase intake of fruits
think both about each individual person's behavior and about population-level
strategies--including food pricing--to reinforce what we're trying to
general pediatrics practice, I often see kids drinking juice from "sippy"
cups or bottles. Excessive drinking of juice drinks--even drinks consisting
of 100% juice--is an important issue.
are in charge of what children are offered, and children can choose
to eat it or not. The notion that children may consume as much juice
as they want is really the wrong message.
show that, in general, sodas and alcoholic beverages add calories to
food calories. Some early research also shows that whole fruit is more
satiating than fruit juice. The more processed the food, the less satisfying
it is for the same number of calories.
you comment on Gary Taubes' article about dietary fat, "What if it's
all a Big Fat Lie?,"16 which appeared in the New York
presents so many controversies that you can "tell the truth"
simply by selectively including or excluding facts, as Taubes appears
to have done. However, scientists do agree that we should eat more fruits
and vegetables and fewer refined carbohydrates and that protein sources
should be lean.
National Institute of Diabetes & Digestive & Kidney Diseases
supported the research.
Heart, Lung, and Blood Institute. Clinical guidelines on the identification,
evaluation, and treatment of overweight and obesity in adults: the evidence
report. Bethesda (MD): Department of Health and Human Services, National
Institutes of Health, National Heart, Lung, and Blood Institute; 1998.
B, Barnett RA. Volumetrics: feel full on fewer calories. New York: HarperCollins;
B, Barnett RA. The volumetrics weight-control plan: feel full on fewer
calories. New York: HarperTorch; 2003.
BJ, Bell EA. Dietary approaches to the treatment of obesity. Med Clin
North Am 2000 Mar;84(2):401-18, vi.
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
BJ, Roe LS. Effect of the volume of liquid food infused intragastrically
on satiety in women. Physiol Behav 2002 Aug;76(4-5):623-31.
BJ, Bell EA, Castellanos VH, Chow M, Pelkman CL, Thorwart ML. Energy
density but not fat content of foods affected energy intake in lean
and obese women. Am J Clin Nutr 1999 May;69(5):863-71.
RJ, Johnstone AM, O'Reilly LM, Barton K, Reid C. The effect of covertly
manipulating the energy density of mixed diets on ad libitum food intake
in 'pseudo free-living' humans. Int J Obes Relat Metab Disord 1998 Oct;22(10):980-7.
EA, Castellanos VH, Pelkman CL, Thorwart ML, Rolls BJ. Energy density
of foods affects energy intake in normal-weight women. Am J Clin Nutr
EA, Rolls BJ. Energy density of foods affects energy intake across multiple
levels of fat content in lean and obese women. Am J Clin Nutr 2001 Jun;73(6):1010-8.
DD, ed. Mayo Clinic on healthy weight. Rochester (MN): Mayo Clinic;
MR, Annunziato R, Riddell L, et al. Controlled trial of a nutrition-focused
treatment for weight loss maintenance. Int J Obes Relat Metab Disord
2002 Aug;26 Suppl 1:S24.
TVE, Roe LS, Rolls BJ. Does nutrition information about the energy density
of meals affect food intake in normal-weight women? Appetite 2002 Oct;39(2):137-45.
J, Roberts SB, Dallal G, Saltzman E. High-protein weight-
loss diets: are they safe and do they work? A review of the experimental
and epidemiologic data. Nutr Rev 2002 Jul;60(7 Pt 1):189-200.
- St Jeor
ST, Howard BV, Prewitt TE, Bovee V, Bazzarre T, Eckel RH. Dietary protein
and weight reduction: a statement for healthcare professionals from
the Nutrition Committee of the Council on Nutrition, Physical Activity,
and Metabolism of the American Heart Association. Circulation 2001 Oct
G. What if it's all a big fat lie? New York Times 2002 Jul 7;Sect. 6:22(col.
Health Systems contents list >>
full contents list >>