Appropriate Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults

1
Appropriate Intervention Strategies for Weight
Loss and Prevention of Weight Regain for Adults

• Medicine Science in Sports Exercise Volume
  33(12) December 2001 pp 2145-2156

2
Introduction

• 56 25 kg/m2 BMI
• 23 30 kg/m2 BMI
• 100 billion annually to treat obesity related
  conditions

Center of Disease Control
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Identifying

• What is the advantage of using BMI?
• What is the disadvantage of using BMI?
• Why is percent body fat not used?

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Fat Distribution
6
Fat Distribution

• Fat distribution and intra-abdominal fat
• How do you measure it?
• Waist/Abdominal circumference
• Abdomen 102 cm (40 inches) in men
• Abdomen 88 cm (35 inches) in women

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Magnitude

• How much weight loss is significant?
• Initially, 5-10
• Eventually, 10

8
Diet

• Common to reduce energy intake by 1,000-1,500
  kcals/day
• Goal reduce intake by 500-1000 kcals/day

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Diet

• Resting Metabolic Rate 1 kcal/kg/hr
• 90.7 kg (200 lbs) 2, 176.8 kcals/day
• With an intake of 1000-1500 kcals/day there would
  be an energy deficit of 676-1,176 kcals per day
• 4,737-8232 kcals/week or 1-2 pounds

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Very-low Calories Diets

• How low is very low?
• Do they work? Are they better other, higher
  calorie diets?

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Macronutrient

• Which is more important when it comes to helping
  a person lose weight, the type of food or the
  amount of food in the diet?
• Why?

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Reduced Fat Intake

• What is the reason that reducing the amount of
  fat in the diet is effective for weight loss?
• The National Weight Control Registry found 24
  fat in the diets of people who were successful
  with weight loss.
• A 10 reduction in fat intake can have a
  significant impact on the energy balance and body
  weight over the long-term.

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Willett WC  Leibel RL Dietary fat is not a
major determinant of body fat.The American
Journal of Medicine 2002 Dec 30 113 Suppl 9B
47S-59S

• The percentage of energy from fat in diets has
  been thought to be an important determinant of
  body fat, and several mechanisms have been
  proposed. Comparisons of diets and the prevalence
  of obesity between affluent and poor countries
  have been used to support this relationship, but
  these contrasts are seriously confounded by
  differences in physical activity and food
  availability. Within areas of similar economic
  development, regional intake of fat and
  prevalence of obesity have not been positively
  correlated. Randomized trials are the preferable
  method to evaluate the effect of dietary fat on
  adiposity and are feasible because the number of
  subjects needed is not large. In short-term
  trials, a modest reduction in body weight is
  typically seen in individuals randomized to diets
  with a lower percentage of calories from fat.
  However, compensatory mechanisms appear to
  operate, because in randomized trials lasting
  or1 year, fat consumption within the range of
  18 to 40 of energy appears to have little if
  any effect on body fatness. The weighted mean
  difference was -0.25 kg overall and 1.8 kg
  (i.e., less weight loss on the low-fat diets) for
  trials with a control group that received a
  comparable intensity intervention. Moreover,
  within the United States, a substantial decline
  in the percentage of energy from fat during the
  last 2 decades has corresponded with a massive
  increase in the prevalence of obesity. Diets high
  in fat do not appear to be the primary cause of
  the high prevalence of excess body fat in our
  society, and reductions in fat will not be a
  solution.

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Protein

• Why might a high protein diet be helpful with
  weight loss?
• Increase thermogenesis and satiety

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Dansinger ML  Gleason JA  Griffith JL  Selker
HP  Schaefer EJ Comparison of the Atkins,
Ornish, Weight Watchers, and Zone diets for
weight loss and heart disease risk reduction a
randomized trial.JAMA 2005 Jan 5 293(1) 43-53

• 160 overweight people were randomly assigned to
  one of the four diets. They followed a supervised
  program for two months and were left to continue
  the diets on their own.
• After only two months, 22 percent quit the study.
  After a year, 35 percent dropped out of Weight
  Watchers and the Zone diets, and 50 percent quit
  the Atkins and Ornish plans.
• People who stayed on their diet for a full year
  did experience weight loss.
• 6 percent weight loss for the Ornish program (low
  fat)
• 5 percent weight loss for those on both Weight
  Watchers and the Zone diets
• 4 percent weight loss for Atkins dieters (low
  carb)

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Astrup A  Meinert Larsen T  Harper A Atkins
and other low-carbohydrate diets hoax or an
effective tool for weight loss?Lancet 2004 Sep
4-10 364(9437) 897-9

• CONTEXT The Atkins diet books have sold more
  than 45 million copies over 40 years, and in the
  obesity epidemic this diet and accompanying
  Atkins food products are popular. The diet claims
  to be effective at producing weight loss despite
  ad-libitum consumption of fatty meat, butter, and
  other high-fat dairy products, restricting only
  the intake of carbohydrates to under 30 g a day.
  Low-carbohydrate diets have been regarded as fad
  diets, but recent research questions this view.
• STARTING POINT A systematic review of
  low-carbohydrate diets found that the weight loss
  achieved is associated with the duration of the
  diet and restriction of energy intake, but not
  with restriction of carbohydrates. Two groups
  have reported longer-term randomised studies that
  compared instruction in the low-carbohydrate diet
  with a low-fat calorie-reduced diet in obese
  patients (N Engl J Med 2003 348 2082-90 Ann
  Intern Med 2004 140 778-85). Both trials showed
  better weight loss on the low-carbohydrate diet
  after 6 months, but no difference after 12
  months.
• WHERE NEXT? The apparent paradox that ad-libitum
  intake of high-fat foods produces weight loss
  might be due to severe restriction of
  carbohydrate depleting glycogen stores, leading
  to excretion of bound water, the ketogenic nature
  of the diet being appetite suppressing, the high
  protein-content being highly satiating and
  reducing spontaneous food intake, or limited food
  choices leading to decreased energy intake.
  Long-term studies are needed to measure changes
  in nutritional status and body composition during
  the low-carbohydrate diet, and to assess fasting
  and postprandial cardiovascular risk factors and
  adverse effects. Without that information,
  low-carbohydrate diets cannot be recommended

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Science of Sport Are the Atkins, Zone, and South
Beach Diets Slowing you Down?By Kimberly
Mueller-Brown, MS, RD

• Here are the top ten reasons why high
  carbohydrate diets win the race.
• 10. Low carbohydrate diets leave you mentally
  drained
• 9. Low carbohydrate diets trigger premature
  muscle fatigue during exercise
• 8. Low carbohydrate diets compromise immune
  function
• 7. Low carbohydrate diets affect mood
• 6. Low carbohydrate diets are often deficient in
  essential nutrients
• 5. Low carbohydrate diets slow muscle recovery
• 4. Low carbohydrate diets increase risk for
  muscle injury during training
• 3. Low carbohydrate diets increase risk for
  kidney stones
• 2. Low carbohydrate diets can diminish bone
  healt
• 1. Low carbohydrate diets can trigger joint pain

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Science of Sport Are the Atkins, Zone, and South
Beach Diets Slowing you Down?By Kimberly
Mueller-Brown, MS, RD

• Traditional guidelines posted by the American
  Dietetic Association recommend that 45-65 of
  total calories be consumed in the form of
  carbohydrates, with guidelines for endurance
  athletes focusing on the latter end of these
  recommendations during training and competition.
  The carbohydrate intake of elite distance runners
  in the United States, Netherlands, Australia, and
  Southern Africa have been measured at 49, 50,
  52, and 50 respectively. Perhaps the most
  decorated distance runners in the world, however,
  are the Kenyan runners who reportedly won a
  staggering 40 of all major international middle-
  and long-distance competitions from 1987-1997.6
  Interestingly, Kenyan runners have a carbohydrate
  composition that tower over their competition
  with measurements reporting 75 or 10.4 grams
  carbohydrate per kg of body mass, which may lead
  one to argue that running success and
  carbohydrate intake are directly related.

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Exercise Recommendations

• Is a combination of diet and exercise the most
  effective approach to weight loss?
• What about maintenance and exercise?
• What about weight loss and exercise alone?
• Ross, et al 2000.

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Responders
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Exercise

• What is meant by responders and
  non-responders?
• 6.8 times greater difference between pairs of
  twins compared to within pairs of twins.
• Somatotype
• Gender difference?

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Exercise Prescription

• Duration. Is 30 minutes, most days of the week
  enough?
• Research findings
• 200-300 minutes per week
• 2000 kcals per week
• (60 minutes per day)
• Are those amounts realistic?
• Progression
• Other benefits to exercise

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Exercise Prescription

• Intensity. Is 55-69 enough?
• Intermittent exercise. Is it effective?

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Exercise Prescription

• Physical activity (lifestyle activity) or
  structured/formal exercise? Does it matter?

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Resistance Training

• Does resistance training increase fat-free mass?
• Does an increase in FFM increase resting
  metabolic rate?
• Does resistance training significantly help with
  weight loss?
• Why or why not?

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Resistance Training and REE
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Pharmacological Weight Loss

• BMI 30 or BMI 27 w/ risk factors
• Appetite suppresants
• e.g. Merida (Subutramine)
• Fat absorption inhibitor
• e.g. Xenical (orlistat)
• Over the counter options
• buyer beware
• Maximize weight loss reached at 6 months

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Drugs in the treatment of obesity sibutramine,
orlistat and rimonabant. Rubio MA Gargallo M
Isabel Millán A Moreno B Public health
nutrition (Public Health Nutr) 2007 Oct 10(10A)
1200-5 BACKGROUND Modification of lifestyle is
the main therapeutical approach in the treatment
of obesity, but use to fail on long terms of
time. Addition of anti-obesity drugs allows
keeping the weight loss during years and
improving obesity-related comorbidities.
METHODS This review is an actualization on
efficacy, safety and tolerability of the approved
drugs on the long-term treatment of obesity
(orlistat and sibutramine). New indications and
effects of their use far beyond the weight loss
are as well commented. Finally, potential
benefits of the administration of CB1 antagonist
rimonabant on the weight loss and cardiometabolic
risk factors are analysed in detail.
DISCUSSION A decade of experience on the use
of orlistat and sibutramine has demonstrated
their higher efficacy on the weight loss when
compared to placebo either on adult or teenage
population as well as safety and tolerability on
long-term administration. Beneficial effects on
the lipid profile, glycosilated haemoglobin on
diabetic patients, blood pressure and levels of
inflammatory cytokines, contribute to decrease
the cardiovascular risk on obese patients. Phase
III clinical trials using rimonabant show
additional benefits to the expected weight loss,
mainly reducing visceral fat and cardiometabolic
risk factors. CONCLUSION Pharmacological
treatment of obesity must be considered as a
therapeutical tool that has to be used together
with long-term lifestyle changes, contributing to
the body weight reduction as well as to the
improvement of the cardiometabolic risk related
to obesity.
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Behavioral Recommendations

• Maintain contact
• Training in behavioral concepts
• Self-monitoring of eating and exercise
• Portion control diets
• Strategies that my facilitate the adoption and
  maintenance of exercise behaviors

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Summary of ACSM Recommendations
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1. It is recommended that individuals with a body
mass index 25 kgm2 consider reducing their body
weight, especially if this level of body weight
is accompanied by an increase in abdominal
adiposity. Individuals with a body mass index
30 kgm-2 are encouraged to seek weight loss
treatment (see Table 1). Although it is
recognized that body mass index may misclassify
the health risk of very active and/or lean
individuals, the use of body mass index provides
a meaningful clinical assessment of health risk.
Moreover, although it is also recognized that
more sophisticated measures of body composition
are available, there is no consensus on the
absolute amount of body fatness at which health
risk increases. 2. It is recommended that
overweight and obese individuals target reducing
their body weight by a minimum of 5-10 and
maintain at least this magnitude of weight loss
long-term. This amount of weight loss is
consistent with what is attainable with standard
weight loss programs that focus on modifying
eating and exercise behaviors, and this amount of
weight loss has been shown to be associated with
improvements in risk factors and a reduced
likelihood of chronic diseases including coronary
heart disease, type 2 diabetes, hypertension, and
hyperlipidemia.
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3. It is recommended that individuals strive for
long-term weight maintenance and the prevention
of weight regain over the long-term, especially
when weight loss is not desired, or when
attainment of ideal body weight is not
achievable. Prevention of weight gain or weight
regain has been defined as maintaining a body
weight that is within 2.3 kg (5 pounds) of one's
current weight (92,93). 4. It is recommended
that weight loss programs target changing both
eating and exercise behaviors, as sustained
changes in both behaviors have been shown to
result in significant long-term weight loss.
Moreover, it is important for programs targeting
modifications in these behaviors to incorporate
strong behavioral modification strategies to
facilitate the adoption and maintenance of the
desired changes in behavior. 5. It is
recommended that overweight and obese individuals
reduce their current level of energy intake by
500-1000 kcal/day to achieve weight loss and that
this be combined with a reduction in dietary fat
to recommended that an individualized level of
energy intake be established that prevents weight
regain after initial weight loss, while
maintaining a low-fat diet (30 of total energy
intake) (55). Additional research is needed with
regard to changes in other macronutrients and
long-term weight loss.
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6. It is recommended that overweight and obese
individuals progressively increase to a minimum
of 150 min of moderate intensity physical
activity per week, as this level of exercise may
have a positive impact on health in overweight
and obese adults. However, for long-term weight
loss, overweight and obese adults should
eventually progress to higher amounts of exercise
(e.g., 200-300 minwk-1 or 2000 kcalwk-1 of
leisure-time physical activity). Table 2 provides
specific information regarding energy expenditure
for various modes of physical activity. 7. It
is recommended that resistance exercise
supplement the endurance exercise program in
overweight and obese adults that are undertaking
modest reductions in energy intake to lose
weight. Resistance exercise should focus on
improving muscular strength and endurance in this
population. 8. It is recommended that
pharmacotherapy for weight loss only be used in
individuals with a body mass index 30 kgm2, or
with a body mass index 27 kgm-2 in the presence
of additional comorbidities. In addition, it is
recommended that weight loss medications only be
used in combination with a strong behavioral
intervention that focuses on modifying eating and
exercise behaviors, and be used under the
supervision of a physician.
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Other Weight Loss Studies
37
Kay SJ  Fiatarone Singh MA  The influence of
physical activity on abdominal fat a systematic
review of the literature. Obesity reviews an
official journal of the International Association
for the Study of Obesity (Obes Rev) 2006 May
7(2) 183-200 The relationship between excess
abdominal adipose tissue, metabolic and
cardiovascular health risk has stimulated
interest in the efficacy of physical activity in
specifically perturbing this adipose depot. The
evolution of imaging techniques has enabled more
direct measurement of changes in abdominal and
visceral fat. The purpose of this summary was to
systematically review the relationship between
physical activity and abdominal fat. METHODS
Database searches were performed on MEDLINE,
CINAHL, SPORT DISCUS and PUBMED, from 1985 to
2005 with keywords "exercise", "abdominal fat"
and "visceral fat". RESULTS Nineteen
randomized controlled trials (RCTs) and eight
non-randomized controlled trials were selected.
In RCTs using imaging techniques to measure
change in abdominal fat in overweight or obese
subjects, seven out of 10 studies (including
three trials with type 2 diabetics) reported
significant reductions compared with controls.
Reductions in visceral and total abdominal fat
may occur in the absence of changes in body mass
and waist circumference. Waist-to-hip ratio is
not a sensitive measure of change in regional
adiposity in exercise studies. No studies fulfill
the Consolidated Standards of Reporting Trials
(CONSORT) statement's criteria for the highest
quality of randomized trial however, many
studies were in progress or published before the
opportunity to comply with these recommendations.
Therefore, limited evidence from a number of
studies suggests a beneficial influence of
physical activity on reduction in abdominal and
visceral fat in overweight and obese subjects
when imaging techniques are used to quantify
changes in abdominal adiposity. More rigorous
studies are needed to confirm these observations.
38
Volek JS  Vanheest JL  Forsythe CE  Diet and
exercise for weight loss a review of current
issues. Sports medicine (Auckland, N.Z.) (Sports
Med) 2005 35(1) 1-9 Obesity is a fast growing
epidemic that is primarily due to environmental
influences. Nutrition and exercise represent
modifiable factors with a major impact on energy
balance. Despite considerable research, there
remains continued debate regarding the energy
content and the optimal macronutrient
distribution for promoting healthy and effective
weight loss. Low-fat diets have been advised for
many years to reduce obesity. However, their
effectiveness has been recently challenged,
partly because the prevalence of obesity
continues to rise despite reductions in fat
intake. There are also concerns regarding the
methodology of clinical trials showing benefits
of fat reduction on weight loss. Although often
viewed as a fad diet, very low-carbohydrate
(ketogenic) diets are very popular and several
recent clinical trials indicate they are more
effective at promoting short-term weight loss and
improving characteristics of the metabolic
syndrome than low-fat diets. However, there is a
need to obtain long-term safety and efficacy
data. Clearly, weight loss can be achieved with a
variety of diet interventions but the effects on
other health-related aspects also need to be
considered and studied in more detail. Exercise
can have positive effects on weight loss, weight
control and overall general health, although
debate exists concerning the most effective mode,
duration and intensity of exercise required to
achieve these effects. Importantly, any effective
weight control treatment must consider a
life-long plan or there will likely be weight
regain. Perhaps the most challenging, but
rewarding, question that faces researchers is how
to predict individual responses to diet and
exercise interventions.
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Curioni CC  Lourenço PM  Long-term weight loss
after diet and exercise a systematic
review. International journal of obesity (2005)
(Int J Obes (Lond)) 2005 Oct 29(10)
1168-74 OBJECTIVE To assess the effectiveness
of dietary interventions and exercise in
long-term weight loss in overweight and obese
people. DESIGNA systematic review with
meta-analysis. SUBJECTS Overweight and obese
adults-18 years old or older with body mass index
(calculated as weight divided by the square of
height in meters)25. DATA SOURCE Medline,
Cochrane Library and Lilacs databases up to March
2003. Also, published reviews and all relevant
studies and their reference lists were reviewed
in search for other pertinent publications. No
language restrictions were imposed. STUDY
SELECTION Randomised clinical trials comparing
diet and exercise interventions vs diet alone.
All trials included a follow-up of 1 y after
intervention. DATA EXTRACTION Two reviewers
independently abstracted data and evaluated the
studies' quality with criteria adapted from the
Jadad Scale and the Delphi list. DATA
SYNTHESIS The estimate of the intervention's
effect size was based on the differences between
the comparison groups, and then the overall
effect was calculated. A chi-squared test was
used to assess statistical heterogeneity. RESULTS
A total of 33 trials evaluating diet, exercise
or diet and exercise were found. Only 6 studies
directly comparing diet and exercise vs diet
alone were included (3 additional studies
reporting repeated observations were excluded).
The active intervention period ranged between 10
and 52 weeks across studies. Diet associated with
exercise produced a 20 greater initial weight
loss. (13 kg vs 9.9 kg z1.86-p0.063, 95CI).
The combined intervention also resulted in a 20
greater sustained weight loss after 1 y (6.7 kg
vs 4.5 kg z1.89-p0.058, 95CI) than diet
alone. In both groups, almost half of the initial
weight loss was regained after 1 y. CONCLUSION
Diet associated with exercise results in
significant and clinically meaningful initial
weight loss. This is partially sustained after 1
y.
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Elfhag K  Rössner S  Who succeeds in
maintaining weight loss? A conceptual review of
factors associated with weight loss maintenance
and weight regain. Obesity reviews an official
journal of the International Association for the
Study of Obesity (Obes Rev) 2005 Feb 6(1)
67-85 Weight loss is difficult to achieve and
maintaining the weight loss is an even greater
challenge. The identification of factors
associated with weight loss maintenance can
enhance our understanding for the behaviours and
prerequisites that are crucial in sustaining a
lowered body weight. In this paper we have
reviewed the literature on factors associated
with weight loss maintenance and weight regain.
We have used a definition of weight maintenance
implying intentional weight loss that has
subsequently been maintained for at least 6
months. According to our review, successful
weight maintenance is associated with more
initial weight loss, reaching a self-determined
goal weight, having a physically active
lifestyle, a regular meal rhythm including
breakfast and healthier eating, control of
over-eating and self-monitoring of behaviours.
Weight maintenance is further associated with an
internal motivation to lose weight, social
support, better coping strategies and ability to
handle life stress, self-efficacy, autonomy,
assuming responsibility in life, and overall more
psychological strength and stability. Factors
that may pose a risk for weight regain include a
history of weight cycling, disinhibited eating,
binge eating, more hunger, eating in response to
negative emotions and stress, and more passive
reactions to problems.
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Effects of the Amount of Exercise on Body Weight,
Body Composition, and Measures of Central
Obesity. Cris A. Slentz, PhD et al Arch Intern
Med. 200416431-39.

• Background  Obesity is a major health problem
  due, in part, to physical inactivity. The amount
  of activity needed to prevent weight gain is
  unknown.
• Objective  To determine the effects of different
  amounts and intensities of exercise training.
• Design  Randomized controlled trial (February
  1999July 2002).
• Setting and Participants  Sedentary, overweight
  men and women (aged 40-65 years) with mild to
  moderate dyslipidemia were recruited from Durham,
  NC, and surrounding communities.
• Interventions  Eight-month exercise program with
  3 groups (1) high amount/vigorous intensity
  (calorically equivalent to approximately 20 miles
  32.0 km of jogging per week at 65-80 peak
  oxygen consumption) (2) low amount/vigorous
  intensity (equivalent to approximately 12 miles
  19.2 km of jogging per week at 65-80), and
  (3) low amount/moderate intensity (equivalent to
  approximately 12 miles 19.2 km of walking per
  week at 40-55). Subjects were counseled not to
  change their diet and were encouraged to maintain
  body weight.
• Main Outcome Measures  Body weight, body
  composition (via skinfolds), and waist
  circumference.

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• Results  Of 302 subjects screened, 182 met
  criteria and were randomized and 120 completed
  the study. There was a significant (Pdose-response relationship between amount of
  exercise and amount of weight loss and fat mass
  loss. The high-amount/vigorous-intensity group
  lost significantly more body mass (in mean SD
  kilograms) and fat mass (in mean SD kilograms)
  (-2.9 2.8 and -4.8 3.0, respectively) than
  the low-amount/moderate-intensity group (-0.9
  1.8 and -2.0 2.6, respectively), the
  low-amount/vigorous-intensity group (-0.6 2.0
  and -2.5 3.4, respectively), and the controls
  (1.0 2.1 and 0.4 3.0, respectively). Both
  low-amount groups had significantly greater
  improvements than controls but were not different
  from each other. Compared with controls, all
  exercise groups significantly decreased
  abdominal, minimal waist, and hip circumference
  measurements. There were no significant changes
  in dietary intake for any group.
• Conclusions  In nondieting, overweight subjects,
  the controls gained weight, both low-amount
  exercise groups lost weight and fat, and the
  high-amount group lost more of each in a
  dose-response manner. These findings strongly
  suggest that, absent changes in diet, a higher
  amount of activity is necessary for weight
  maintenance and that the positive caloric
  imbalance observed in the overweight controls is
  small and can be reversed by a modest amount of
  exercise. Most individuals can accomplish this by
  walking 30 minutes every day.

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Successful Weight Loss Maintenance. Wing, Rena
R. Hill, James O. Annual Review of Nutrition v.
21 (2001) p. 323-41

• INTRODUCTION
• Obesity is a major health problem in the United
  States, with over 50 of Americans classified as
  overweight or obese. Many of these individuals
  are attempting to lose weight (39). However, the
  perception of the general public is that
  long-term reduction in body weight is difficult
  to achieve. The goal of this chapter is to
  summarize the information available on successful
  weight loss maintenance. How many achieve this
  goal? How do they do it? What are the
  consequences? In describing successful weight
  loss maintainers, we draw heavily on findings
  from the National Weight Control Registry (NWCR),
  a registry of individuals who have been extremely
  successful at long-term weight loss maintenance.

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Successful Weight Loss Maintenance.

• It is important that a consensus be reached on a
  definition for successful weight loss
  maintenance. Our recommendation is that an
  intentional weight loss of greater than or equal
  to 10 of initial body weight that is maintained
  at least 1 year be considered success. According
  to this definition, approximately 20 or more of
  individuals who attempt weight loss would be
  "successful." Although the NWCR does not provide
  information about how many people achieve
  long-term weight loss success, it does provide
  information about strategies used to achieve and
  maintain a weight loss. With regard to weight
  loss, the most obvious conclusion from the NWCR
  is that weight loss should include both changing
  diet and increasing physical activity. We do not,
  however, see any particular type of diet
  modification to achieve the weight loss that is
  common to these successful weight loss
  maintainers.

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Successful Weight Loss Maintenance.

• We believe that strategies for weight loss
  maintenance may be the key to long-term weight
  management success. We find three behaviors in a
  vast majority of NWCR subjects. First, these
  subjects engage in high levels of physical
  activity. The amount of physical activity that
  facilitates successful weight loss maintenance
  may be closer to 1 h/day rather than the 30 min
  three times per week suggested in recommendations
  to the general public. Consequently, we may need
  to increase our physical activity goals in
  obesity treatment programs.

46
Physical activity, total and regional obesity
dose-response considerations

• ROSS, ROBERT JANSSEN, IAN
• Medicine and Science in Sports and Exercise
  Volume 33(6) Supplement June 2001 pp S521-S527

47
Purpose This review was undertaken to determine
whether exercise-induced weight loss was
associated with corresponding reductions in
total, abdominal, and visceral fat in a
dose-response manner. Methods A literature
search (MEDLINE, 1966-2000) was performed using
appropriate keywords to identify studies that
consider the influence of exercise-induced weight
loss on total and/or abdominal fat. The reference
lists of those studies identified were
cross-referenced for additional studies.
Results Total fat. Review of available
evidence suggested that studies evaluating the
utility of physical activity as a means of
obesity reduction could be subdivided into two
categories based on study duration. Short-term
studies (16 wk, N 20) were characterized by
exercise programs that increased energy
expenditure by values double (2200 vs 1100
kcalwk-1) that of long-term studies (26 wk, N
11). Accordingly, short-term studies report
reductions in body weight (-0.18 vs -0.06
kgwk-1) and total fat (-0.21 vs -0.06 kgwk-1)
that are threefold higher than those reported in
long-term studies.
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Results (continued) Moreover, with respect to
dose-response issues, the evidence from
short-term studies suggest that exercise-induced
weight loss is positively related to reductions
in total fat in a dose-response manner. No such
relationship was observed when the results from
long-term studies were examined. Abdominal fat.
Limited evidence suggests that exercise-induced
weight loss is associated with reductions in
abdominal obesity as measured by waist
circumference or imaging methods however, at
present there is insufficient evidence to
determine a dose-response relationship between
physical activity, and abdominal or visceral fat.
Conclusion In response to well-controlled,
short-term trials, increasing physical activity
expressed as energy expended per week is
positively related to reductions in total
adiposity in a dose-response manner. Although
physical activity is associated with reduction in
abdominal and visceral fat, there is insufficient
evidence to determine a dose-response
relationship.
49
Physical activity in the prevention of obesity
current evidence and research issuesDiPietro,
Loretta Med. Sci. Sports Exerc., 31
(11)S542-S546, 1999.

• Purpose The relation between habitual physical
  activity and the prevention of overweight and
  obesity in adults based on the evidence from the
  epidemiologic literature is described.
• Methods Literature was reviewed of current
  findings from large population-based studies of
  forward directionality in which physical activity
  was considered as a primary study factor.
• Results The longitudinal evidence suggests that
  habitual physical activity plays more of a role
  in attenuating age-related weight gain, rather
  than in promoting weight loss. Moreover, recent
  data suggest that increasing amounts of physical
  activity may be necessary to effectively maintain
  a constant body weight with increasing age.
• Conclusion Over decades, small savings in excess
  weight gain accumulate into net savings that may
  be quite meaningful with regard to minimizing the
  risk associated with obesity-related disorders.
  The question remains as to how important
  maintaining a constant body weight through middle
  age and into older age is to healthy,
  already-active people of normal body weight.

50
Reductions in portion size and energy density of
foods are additive and lead to sustained
decreases in energy intake1,2,3Barbara J Rolls,
Liane S Roe and Jennifer S MeengsAmerican
Journal of Clinical Nutrition.

• Background When the portion size and energy
  density (in kcal/g) of a food are varied
  simultaneously in a single meal, each influences
  energy intake independently.
• Objective We aimed to determine how the effects
  of portion size and energy density combine to
  influence energy intake and satiety over multiple
  meals for 2 d.
• Design In a crossover design, 24 young women
  were provided with meals and snacks for 2
  consecutive days per week for 4 wk all foods
  were consumed ad libitum. Across the 4 sessions,
  the subjects were served the same 2 daily menus,
  but all foods were varied in portion size and
  energy density between a standard level (100)
  and a reduced level (75).
• Results Reducing the portion size and energy
  density of all foods led to significant and
  independent decreases in energy intake over 2 d
  (P to a 10 decrease in energy intake (231 kcal/d),
  and a 25 decrease in energy density led to a 24
  decrease in energy intake (575 kcal/d). The
  effects on energy intake were additive and were
  sustained from meal to meal. Despite the large
  variation in energy intake, there were no
  significant differences in the ratings of hunger
  and fullness across conditions over the 2 d.
• Conclusions Reductions in portion size and
  energy density independently decreased ad libitum
  energy intake in women when commonly consumed
  foods were served over 2 d. Reductions in both
  portion size and energy density can help to
  moderate energy intake without increased hunger.