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Medscape on dieting



 
 
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  #1  
Old March 2nd, 2004, 01:17 PM
Tabi Kasanari
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Posts: n/a
Default Medscape on dieting

Medscape is running a series of articles with a sensible overview of
weight-reduction schemes. Here's the first part in the series. See the link
at the end for the references. I don't plan on posting the remaining parts.

Note: Medscape requires registration, but is free.

Making Scientific Sense of Different Dietary Approaches, Part 1: Meeting
Dietary Needs, Achieving Weight Loss

George L. Blackburn, MD, PhD
Medscape Diabetes & Endocrinology 6(1), 2004. c 2004 Medscape

Posted 02/26/2004
Introduction
The greater the prevalence of obesity, the more compelling the allure of
dietary approaches that promise fast and relatively easy weight loss. Diets
are big news in the United States, where 63% of men and 55% of women are
overweight or obese.[1] They're also big business -- a $30 billion a year
industry[2] made up of products and services that run the gamut from videos
to supplements to sugar-free ice cream. Though some of these offerings are
based on good science and are safe and effective, most are nothing more than
useless, while still others are untested or even dangerous. Desperate
dieters, however, are quick to believe anecdotal accounts and
unsubstantiated claims of quick success.

Those who fail to achieve their ideal of svelte good health often wind up as
part of another burgeoning market: the $92.6 billion (in 2002 dollars) in
annual medical expenditures attributed to overweight and obesity -- a figure
up from $78.5 billion in 1998.[3] Public health recommendations call for
weight loss in those who are overweight and have associated medical
conditions and in those who are obese. The optimal means to that end,
however, is a subject of great controversy in both the lay press and the
medical literature. Even the U.S. Department of Agriculture's Food Guide
Pyramid,[4] developed to help Americans make dietary choices that maintain
good health and reduce the risk of chronic disease, has been under scrutiny
and is in the process of being revised.


Current Consensus
The current consensus is that obesity in most individuals is a
multifactorial disorder caused by a combination of environmental and genetic
factors. Despite the complexities of investigating gene/environment
interactions, scientific evidence suggests that genetic variation influences
the ability to lose weight, the total amount of fat lost, the preferential
reduction of abdominal fat stores, and changes in disease risk factors in
response to alterations in energy balance.

The balance between energy intake and energy expenditure, which is regulated
by interactions between environmental and genetic factors, determines body
weight. Family-based and case-control studies suggest that genetic variation
affects responses to environmental and lifestyle changes in energy balance.
Maintenance of stable body weight is achieved via a biological process known
as energy homeostasis, which matches cumulative energy intake to expenditure
over time.

Energy homeostasis involves humoral signals, such as leptin, that create a
circuit between peripheral tissues involved in energy storage and
utilization and central networks controlling energy balance. Obesity is the
most common disorder of energy homeostasis, and because of its increasing
prevalence and strong links to metabolic and cardiovascular diseases, is a
leading cause of mortality worldwide.[5] Understanding how defects in this
homeostatic system cause obesity is critical for the development of new and
more effective forms of therapy.[6,7]


Wide Variations in Individual Responses
Fat, if eaten in excess of energy needs, will make a person overweight or
obese. So will excess intake of carbohydrates. The Evidence-based Guidelines
issued by the National Institutes of Health[8,9] call for weight loss by
simultaneously restricting caloric intake and increasing physical
activity.[10] Many studies demonstrate that obese adults can lose about 1 lb
per week and achieve a 5% to 15% weight loss by consuming 500 to 1000 kcal a
day less than the caloric intake required for the maintenance of their
current weight[8,9] -- a goal that can be best achieved by reducing portion
sizes, minimizing snacks and desserts, and replacing high-fat and
high-calorie foods with lower-fat and lower-calorie choices.

Weight loss, achieved via caloric restriction and increased physical
activity, is the most common treatment prescribed for obesity. Adherence --
measured by such variables as number of weight loss classes attended, degree
of caloric deficit, and length of time spent exercising -- has a partial
influence on outcomes. But even under controlled experimental conditions
with complete adherence, changes in energy balance result in wide
heterogeneity in responses.

Studies suggest considerable interindividual variation in response to
standardized obesity treatments. For example, in middle-aged women, a
16-week, 1200 kcal/day diet resulted in an average weight loss of 9.6 } 3.0
kg (10.7% of initial body weight), with a wide range of weight loss from
6.5% to 16.7% of initial body weight.[11] Controlled energy deficit
interventions showed similar heterogeneity. For example, the amount of fat
lost, measured by dual energy x-ray absorptiometry (DXA), ranged from
3.1-12.4 kg in young women fed a very low-calorie diet (382 kcal/day) for 28
days on an inpatient unit.[12,13] In young men, the mean loss of body weight
after a total energy deficit of 58,317 kcal induced by exercise training was
5 kg, with a range of 1-8 kg.[14]

Experimental as well as clinical data support these outcomes. Among 9
different strains of mice subjected to a high-fat diet for 7 weeks, there
was a 6-fold difference in adiposity gain between the most sensitive and the
most resistant strains.[15] In young men, overfeeding by 1000 kcal/day for
100 days resulted in a mean weight gain of 8.1 kg, but also a 3-fold
difference between the highest and lowest gainers.[16] Similarly,
overfeeding men and women by 1000 kcal/day for 8 weeks resulted in a range
of weight gain from 1.4-7.2 kg, along with a 10-fold difference (58-687
kcal/day) in fat storage.[17]


The Latest Recommended Daily Allowances (RDAs)
New RDAs for fat, protein, and carbohydrates[18] broaden the recommended
ranges for consuming these nutrients compared with earlier guidelines.
Whereas the latter called for diets with 50% or more of calories from
carbohydrates and 30% or less from fat, the most recent adult reference
intakes specify 45% to 65% of calories from carbohydrates, 20% to 35% from
fat, and 10% to 35% from protein. New guidelines for children are similar to
those for adults, except for a slight increase in the proportion of fat (25%
to 40% of caloric intake) recommended for infants and young children.

The minimum for carbohydrates -- 130 grams per day -- is based on the least
amount needed to produce enough glucose for the brain to function; most
people, however, regularly consume more than that. The upper limit for added
sugars (ie, those found in candy, soft drinks, fruit drinks, pastries, and
other sweets) is 25% of total calories; evidence indicates that people whose
diets are high in such sugars have lower intakes of essential nutrients.


Overview of Macronutrients
Dietary Fat
Fat is a major source of energy for the body and aids in the absorption of
essential vitamins. Dietary fats -- either saturated, monounsaturated, or
polyunsaturated -- are typically found in butter, margarine, vegetable oils,
visible fat on meat and poultry, whole milk, egg yolks, and nuts.

Saturated fats -- usually found in meats, baked goods, fast food, and full
dairy products -- can raise low-density lipoprotein (LDL)-cholesterol levels
and risk of heart attack in certain individuals; so can trans fatty acids, a
form of unsaturated fat used in many margarines and shortenings. Saturated
fats are of no known benefit in preventing chronic disease, nor are they
required at any level in the diet. Because they occur in so many types of
foods, however, an all-out ban would make it very difficult to meet other
nutritional requirements.

Monounsaturated and polyunsaturated fatty acids reduce blood cholesterol as
well as risk of heart disease. Omega-3 (alpha-linolenic) and omega-6
(linoleic) polyunsaturated fatty acids are essential nutrients not
synthesized in the body. The former is found in milk and some vegetable oils
(eg, soybean and flaxseed); the latter in vegetable oils (eg, safflower and
corn oil). Recommended daily intakes for alpha-linolenic acid are 1.6 grams
for men and 1.1 grams for women; recommended intakes for linoleic acid are
17 grams for men and 12 grams for women.

Dietary Protein
The latest RDAs establish age-based requirements for the 9 essential amino
acids found in dietary protein, as well as values for pregnant women,
infants, and children. The recommended level of protein intake for adults
remains unchanged at 0.8 g/kg of body weight. There are no upper intake
levels for protein or the individual amino acids because of
often-conflicting or inadequate data on the potential for high protein diets
to produce chronic or other diseases. Given a lack of data on
overconsumption of some amino acids and protein, the new guidelines also
recommend caution in consuming levels of these nutrients significantly above
those normally found in foods.

Dietary Fiber
Dietary fiber can be found in such foods as cereal bran, sweet potatoes, and
legumes. Pectin, extracted from citrus peel and used as a gel basis for jams
and jellies, is an example of functional fiber, which is isolated or
extracted from natural sources or is synthetic. Recommended intake levels
for fiber, the first established by the Food and Nutrition Board, are based
on studies that show an association between low-fiber diets and increased
risk for heart disease. Other data, though still inconclusive, suggest that
fiber also may aid in weight control and help prevent colon cancer. For
adults 50 years of age or younger, the recommended daily intake for total
fiber (dietary and functional) is 38 grams for men and 25 for women; for men
and women over age 50, the figures are 30 and 21 grams per day,
respectively.[18]

Effects of Macronutrient Intake on Appetite and Energy Balance
Macronutrient intake is one of many factors (eg, neurochemical, gastric
hormone, environmental, emotional) that influence hunger, appetite, and
subsequent food intake -- often on a meal-to-meal basis. Study results on
the effects of macronutrients on appetite and energy balance are summarized
below.

Dietary fat: A number of studies report high degrees of satisfaction and
satiety in subjects on low-fat diets.[19,20] One study found greater
compliance and reduced binge eating on a low-fat diet compared with a
low-calorie diet.[21] A randomized crossover study on voluntary food
consumption in identical twins found that dietary fat had no significant
effect on energy intake; however, analysis of individual foods matched for
energy density, palatability, and fiber showed that energy density and
palatability were significant determinants of energy intake.[22]

Dietary protein: Ten protein preload studies examined the effects of dietary
protein and other macronutrients on later energy intake.[23-28] In 8 of 10
studies, energy intake was lower after the high-protein preload than it was
after the preloads containing the other macronutrients; mean energy intake
was about 9% less with the high-protein preload. Other data suggest that
weight loss from a high-protein diet produces a smaller decline in energy
expenditure than that from a high-carbohydrate diet.

Short-term studies indicate that dietary protein modulates energy intake via
the sensation of satiety and raises total energy expenditure by increasing
the thermic effect of feeding. In studies of diets with fixed energy intake,
satiety and thermic effects did not contribute to weight and fat loss.[29]

Data on body fat loss with ad libitum consumption on high-protein diets are
limited. One 6-month randomized trial comparing 2 ad libitum reduced-fat
diets (30% of total energy) found that subjects on a high-protein diet (25%
of total energy) consumed 18% fewer calories than those on a
high-carbohydrate diet (protein 12% of total energy). The group consuming
the high-protein diet also achieved the greatest fat reduction and weight
loss (8.9 kg vs 5.1kg for the high-carbohydrate group).[30]

Dietary fiber: The majority of studies on soluble or insoluble fiber
indicate that increased intake of either nutrient raises postmeal satiety
and reduces subsequent hunger. Data from studies on ad libitum diets
indicate that consumption of an additional 14 grams per day of fiber for 2
days is associated with a mean decrease in energy intake of 10% and a mean
weight loss of 1.9 kg over 3.8 months. Increased fiber consumption also
appears to reduce energy intake and increase body weight loss in individuals
with obesity.[31]


Conclusion
The latest dietary reference intakes specify how to meet energy and
nutritional needs while minimizing risk of chronic disease. For adults, 45%
to 65% of daily calories should come from carbohydrates; 20% to 35% from
fat; and 10% to 35% from protein. Acceptable RDAs for children are similar
to those for adults, except that infants and younger children need a
slightly higher proportion of fat, ie, 25% to 40% of their caloric intake.
Carbohydrate, fat, and protein all serve as energy sources, and, to some
extent, can be substituted for one another to meet caloric needs.[18]

Part 2 of this column will discuss specific dietary approaches, including a
review of the data on low-carbohydrate, high-protein diets; structured meal
plans; and dairy products and weight control.


References
(see http://www.medscape.com/viewarticle/469768_print)

--
Tabi Kasanari
  #2  
Old March 2nd, 2004, 01:26 PM
Bob in CT
external usenet poster
 
Posts: n/a
Default Medscape on dieting

[cut]

The minimum for carbohydrates -- 130 grams per day -- is based on the
least
amount needed to produce enough glucose for the brain to function;

[cut]

They really need to stop saying this, as it absolutely is not true, and I
can verify by over a year of low carbing.

Overview of Macronutrients
Dietary Fat
Fat is a major source of energy for the body and aids in the absorption
of
essential vitamins. Dietary fats -- either saturated, monounsaturated, or
polyunsaturated -- are typically found in butter, margarine, vegetable
oils,
visible fat on meat and poultry, whole milk, egg yolks, and nuts.

Saturated fats -- usually found in meats, baked goods, fast food, and
full
dairy products -- can raise low-density lipoprotein (LDL)-cholesterol
levels
and risk of heart attack in certain individuals;


They really need to stop saying this too. I never avoid saturated fats,
yet I've increased my HDL (also increased LDL slightly, but lowered my
total chol./HDL ratio).



--
Bob in CT
Remove ".x" to reply
  #3  
Old March 2nd, 2004, 01:52 PM
Pat Paris
external usenet poster
 
Posts: n/a
Default Medscape on dieting

On Tue, 2 Mar 2004 13:17:50 GMT, "Tabi Kasanari"
wrote:

Medscape is running a series of articles with a sensible overview of
weight-reduction schemes. Here's the first part in the series. See the link
at the end for the references. I don't plan on posting the remaining parts.

Good grief, I don't guess you've been following the discussions on
copyright violations, have you? Here's a refresher on the terms you
agreed to when you signed up for Medscape access:

Copyright
We or our partners own the information on Medscape.com. In fact, the
entire contents and design of Medscape.com are protected under U.S.
and international copyright laws. You may look at our Web site online,
download individual articles to your personal or handheld computer for
later reading, and even print a reasonable number of copies of pages
for yourself, your family, or friends. You must not remove any
copyright notices from our materials. We reserve all our other rights.
Among other things, this means you must not sell our information,
rewrite or modify it, redistribute it, put it on your own Web site, or
use it for any commercial purpose without our prior written
permission.

Post a link to the article and/or short exceprts for discussion.
Posting the entire article as you did is a copyright violation and
also violates your agreement with Medscape.
  #4  
Old March 2nd, 2004, 02:13 PM
Roger Zoul
external usenet poster
 
Posts: n/a
Default Medscape on dieting

Bob in CT wrote:
:: [cut]
:::
::: The minimum for carbohydrates -- 130 grams per day -- is based on
::: the least
::: amount needed to produce enough glucose for the brain to function;
:: [cut]
::
:: They really need to stop saying this, as it absolutely is not true,
:: and I can verify by over a year of low carbing.

Agreed.....total nonsense....and do they not know about protein conversion
to glucose?

::
::: Overview of Macronutrients
::: Dietary Fat
::: Fat is a major source of energy for the body and aids in the
::: absorption of
::: essential vitamins. Dietary fats -- either saturated,
::: monounsaturated, or polyunsaturated -- are typically found in
::: butter, margarine, vegetable oils,
::: visible fat on meat and poultry, whole milk, egg yolks, and nuts.
:::
::: Saturated fats -- usually found in meats, baked goods, fast food,
::: and full
::: dairy products -- can raise low-density lipoprotein
::: (LDL)-cholesterol levels
::: and risk of heart attack in certain individuals;
::
:: They really need to stop saying this too. I never avoid saturated
:: fats, yet I've increased my HDL (also increased LDL slightly, but
:: lowered my total chol./HDL ratio).

Agreed again.


  #5  
Old March 2nd, 2004, 10:51 PM
LCer09
external usenet poster
 
Posts: n/a
Default Medscape on dieting


[cut]

The minimum for carbohydrates -- 130 grams per day -- is based on the
least
amount needed to produce enough glucose for the brain to function;

[cut]

They really need to stop saying this, as it absolutely is not true, and I
can verify by over a year of low carbing.


Nah. They'll just say that you're too stupid to eat enough carbs because your
brain obviously isn't functioning. I know, I know, I too could swear that I
have full cognitive powers, but must be wrong. "They" say so.


LCing since 12/01/03-
Me- 265/224/140
& hubby- 310/246/180
  #6  
Old March 2nd, 2004, 11:50 PM
Marsha
external usenet poster
 
Posts: n/a
Default Medscape on dieting


The minimum for carbohydrates -- 130 grams per day -- is based on the
least
amount needed to produce enough glucose for the brain to function;


[cut]

They really need to stop saying this, as it absolutely is not true, and
I can verify by over a year of low carbing.


Wow, my brain hasn't functioned for six months? That's news
to my employer, friends, relatives, whatever...I thought it
was working better.

Marsha/Ohio

  #7  
Old March 3rd, 2004, 12:53 PM
RRzVRR
external usenet poster
 
Posts: n/a
Default Medscape on dieting

LCer09 wrote:

Nah. They'll just say that you're too stupid to eat enough carbs because your
brain obviously isn't functioning. I know, I know, I too could swear that I
have full cognitive powers, but must be wrong. "They" say so.


LCing since 12/01/03-
Me- 265/224/140
& hubby- 310/246/180



FYI, "They"

At the end of the first Medscape article I read:

Funding Information


This column is supported by an unrestricted educational grant from
Slim-Fast.




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