a3 final draft
TRANSCRIPT
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Manipulating Metabolism: Moving Molehills or Mountains?A Look at Metabolic Effects of Saturated Fats, Refined Carbohydrates & Overeating
s a
nutritionist,
I’ve learned and studied the ins and outs of the body, more
specifically in relation to food and metabolic fuels like glucose
(carbohydrates), lipids (fats) and proteins. I’m acutely aware of how involved
the human body is and how ambiguous and complex the phrase “eat
healthy” can be. Everybody is different, from one’s childhood, lifestyle, and
daily responsibilities (or lack thereof) to how an individual’s body
metabolizes, stores, and expends energy. It may be difficult to appreciate
that these two central components of life are co-dependent; a person’s
dietary lifestyle can affect a person’s overall lifestyle and conversely, a
person’s lifestyle can affect a person’s dietary lifestyle. In an effort to help
guide the muddled path of balanced and healthy eating and better equip any
reader with the tools to achieve one’s personal weight and health goals, I’d
like to focus on and explain three chief aspects of nutrition that most people
are faced with on a daily basis and the potential metabolic effects they can
A
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have on the human body. Dietary saturated fats (SFA), refined carbohydrates
and overeating are three facets of nutrition that are closely interrelated and
“feed” off of one another. It’s typical that these three categories are
automatically and negatively associated with what not to do or eat. I ask that
any person reading this will ultimately make their own educated decision on
what they consider to be good or bad for themselves and their own personal
lifestyle.
SATURATED FATS
As most people know, nation-wide and otherwise, the United States is
experiencing its highest level of obesity rates ever recorded and, therefore,
higher rates of acute and chronic obesity-related diseases. Metabolic
Syndrome (MetS), one potential cause of the
aforementioned diseases, is defined as high
visceral adipose composition (abdominal obesity) in
conjunction with two of the four following blood
levels: high blood triglycerides, high blood
pressure, high blood glucose, or a low high-density lipoprotein (HDL)
cholesterol ratio to total cholesterol (TC).4 Some health consequences of
MetS are the increased risk of type II diabetes, cardiovascular disease (CVD),
stroke and other obesity-related diseases.4 Unfortunately, the world-wide
population with MetS is 25% which is currently on the rise since “the
prevalence of MetS parallels the rising rates of obesity.”4 This statistic
represents one-fourth of the world – that’s about 1.8 billion people.6 The
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most prevalent metabolic dysfunctional characteristic among those with
MetS is insulin resistance (IR) which is even more prevalent in those with
MetS who also have high abdominal obesity.4 Insulin resistance is an
unnatural physiological disorder in which cells and tissues become less
sensitive to the presence of insulin which in turn inhibits glucose from
entering said cells and tissues. Over time, glucose will begin to accumulate
in the blood giving rise to blood glucose levels which can significantly
increase the risk of type II diabetes as well as other obesity-related diseases.
According to studies conducted by Susan Jebb, a professor of diet and
population health in the UK, it was concluded that it is more effective to
decrease energy consumption in order to lose weight than to adjust diet
composition in obese people or those with
obesity-related health issues.4 With that
being said, she also denotes in her findings
that since most overweight and obese people
want to lose weight as well as reduce their
health risks, it is equally important to
address fatty acid composition in one’s diet.4
This acknowledgement leads me to the controversial question asked by
health professionals and laymen, alike, are saturated fats actually bad for
you?
In one research study on the relationship between dietary fatty acids and
the development of obesity, IR, and type II diabetes, conducted by Ulf
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Riserus, an associate professor of clinical nutrition and metabolism in
Sweden, it was found that in those with obesity and IR, excess free fatty
acids in the blood were unable to be absorbed and converted into glucose or
stored as triglycerides in the liver, skeletal muscle or adipose tissue.4 This
inability for the liver, muscle and fat tissue to absorb excess free fatty acids
for energy use or storage is what can lead to increased risk of obesity-related
diseases; the body isn’t able to function normally and therefore will react
abnormally and possibly become diseased. Riserus also found in his studies
that the risk of diabetes was inversely proportionate to a diet containing
polyunsaturated fatty acids (PUFAs) and vegetable oils, yet he also stated
that “the effects of different types of dietary fatty acids on obesity and fat
accumulation have not been extensively investigated.” 4
One ongoing debate in the field of nutrition is the controversy between
“good” and “bad” fats and how much a person can consume of each before
health problems arise. The research for and against this subject matter can
get murky given there are several kinds of fats and several ways that they
can be used, stored, or transformed in the body. The research on saturated
fats is difficult to analyze and conduct in human subjects; many research
studies state that their findings are
inconsistent, contradictory and
inconclusive. For instance, one study
conducted on a panel of obese
women who were either insulin-
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sensitive or insulin-resistant, in which they were either fed a high
carbohydrate [60% of total energy consumed (E)], low fat (20% E) diet or a
low carbohydrate (40% E), high fat (40%) diet,
found that the insulin-sensitive women who ate
the high carbohydrate diet lost more weight than
the insulin-sensitive women who ate the high fat
diet. Conversely, the insulin-resistant women who
ate the high fat diet lost more weight than the
insulin-resistant women who ate the high carbohydrate diet. Based on this
study, it can be concluded that the state of insulin sensitivity is a large factor
in the metabolic relationship between weight loss and macronutrient
distribution.4 One of the many suggested fat substitutes for saturated fats
are unsaturated fats (both poly- and mono-), however, “data on the effect of
increasing PUFA at the expense of SFA remain limited and inconsistent.”4 It
seems that some research conducted on both animals and humans suggests
that PUFAs improve weight loss, while other studies suggest increasing SFA
composition in the diet to improve weight loss and health benefits. Berthold
Keletzko, a professor at the University of Munich Medical Center in Germany,
found that those in western countries who consume increased amounts of n-
6 PUFA (vegetable oils) and reduced amounts of n-3 PUFA have an increased
risk of obesity and type 2 diabetes.4
In a research study that was conducted to analyze the metabolic effect of
dietary saturated fat on subject’s fat composition and accumulation, it was
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found, overall, that those who ate a diet high in saturated fat (24%), as
opposed to the average American diet saturated fat composition (12%) and a
diet low in saturated fat (6%), yielded better cholesterol panels, less fat
accumulation, decreased insulin resistance, and an overall decreased risk for
metabolic dysfunction. The reasoning behind this contradictory support for a
high fat diet with 24% SFA is that a diet this high in saturated fatty acids
contains more medium-chain fatty acids (MCFA) as opposed to long-chain
fatty acids (LCFAs); MCFAs can transport from the intestines directly to the
liver for faster oxidation while LCFAs have to be transported through the
blood first before they can be stored and metabolized by the body.
Additionally, MCFAs are less likely to be stored as adipose tissue due to their
efficient oxidation capabilities once inside a cell.1
REFINED CARBOHYDRATES
There are two kinds of carbohydrates: simple and complex. Their names
are definitive of how easily they are
metabolized in the body; simple
(refined) carbohydrates are easily
oxidized by the body while complex
(unrefined) carbohydrates are oxidized
at a slower rate. Being able to absorb
carbohydrates easily and faster may sound efficient and better for the body,
however, this is not the case. Simple carbohydrates are usually high on the
glycemic index while complex carbohydrates are low; the glycemic index is a
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measure of how a food will effect blood glucose and insulin levels. As blood
glucose increases, the release of insulin will increase accordingly since
insulin is the mechanism by which glucose is able to be absorbed into cells to
make ATP (energy). Overtime, if there is enough glucose in the blood, the
body begins to become resistant to insulin which means that glucose can’t
be absorbed into cells and tissues for fuel and will, therefore, begin to
accumulate in the blood causing rise in blood glucose levels.
According to Ludwig, refined carbohydrates have a negative effect on the
body in that they increase energy storage in fat cells which, as a result,
decreases energy expenditure and increases hunger. Additionally, since the
fat cells absorb the energy consumed, there isn’t anything left to circulate or
oxidize in the body which leads the body to believe that it’s
hungry, possibly starving, resulting in overeating.2 In other
words, the body absorbs and utilizes refined carbohydrate
fuel so quickly, their presence as a metabolic fuel in the blood
stream is too short to maintain a feeling of contentment after
eating which leads to increased hunger and food intake.
One study that analyzed metabolic dysfunction in mice as a
result of high refined carbohydrate-containing diets (HC) found that those fed
a HC diet exhibited “acute and sustained increase in visceral adiposity,
glucose intolerance, low insulin sensitivity [insulin resistance] and
hyperlipidemia [high blood lipids]…”5 Within the same study, evidence
showed that even when food intake and body weight were unchanged, the
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mice on the HC diet had a significant increase in their visceral adiposity (fat
accumulation on vital organs).5 In another study, obese young adults were
put on either a low fat diet or a low-glycemic-load diet (indicative of complex
carbohydrates). Results indicated that subjects on the low-glycemic-load diet
lost more weight and experienced a decrease in percent body fat more so
than those on the low-fat diet. Researchers deduced from these findings that
“reducing the glycemic load might be especially important for achieving
weight loss in individuals with high insulin secretion.”4 Overall, this study
supports the evidence that high-carbohydrate containing diets made up
mostly of refined carbohydrates (those with a high glycemic index
composition) can drastically increase fat tissue in the body (with or without
weight gain) which is strongly correlated with MetS.5
OVEREATING
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There is a misconception understood to be true by some people who are
trying to lose weight that cutting calories is the answer. This method of
weight loss can and is usually successful in
overweight and obese people, however, it is
important to note that an acute decrease in
available fuel in the body can lead to extreme
hunger and increased food intake.2 This is why
dieting isn’t as successful as making a dietary
lifestyle change; people feel limited and cornered when only “allowed” to eat
specific amounts of specific foods. On a psychological level, people,
evolutionarily and naturally, start to resist and do the opposite of what
they’re being told (even within themselves) when they feel like they do not
have choice or control in a situation; this stands true when people address
their dietary habits and composition. People need to have choice and control
over their eating to be successful in the long-run. When people deprive
themselves of food or specific kinds of foods, both a psychological and
physiological effect can occur leading to psychological resistance as well as a
strong physiological drive to eat, which usually leads to indulgences and
overeating.
On a biological and chemical level, without needing to know the exact
chemical structures of carbohydrates, fats or proteins, or the biological
chemical reactions that can occur with or between these macronutrients, the
body is capable of breaking down and absorbing carbohydrates easier than
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fats or proteins. This means that when a person eats, the carbohydrates
consumed will be broken down and used up as ATP (energy) first before fat
or protein will be. In the case of overeating, the body can only break down,
absorb and utilize a certain amount of food before it reaches its threshold.
When this threshold is met, the body will store any excess and unnecessary
energy for later use which means fat will be utilized secondarily, if at all,
resulting in fat accumulation throughout the body. As a note, protein isn’t
our focus in this analysis of macronutrient oxidation and storage because it
is the third and last macronutrient to be used as fuel by the body.
In a study published in The New England Journal of Medicine, researching
the effects diet and lifestyle can have on long-term weight gain, it was
suggested that “dietary quality (the types of foods and beverages
consumed) influences dietary quantity (total calories).”3 These findings were
further supported by the positive correlation observed between increased
consumption of starches and refined carbohydrates with weight gain.3
Ultimately, with overeating, it’s important to consider both the diet
composition, mostly focusing on dietary fats and carbohydrates consumed,
as well as the amount of energy consumed as to not consume more energy
than expended on a daily basis.
FOOD FOR THOUGHT
The body is a tricky, messy, intricate web of
chemical and biological reactions that are meant to
keep everything in balance to keep us healthy and
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alive, however, as we’ve learned, our part in this equation is not that simple.
We, as humans, are perfectly imperfect and it is our duty, to the best of our
abilities, to feed our bodies appropriately so that we can continue living on in
this world and fulfill our individual purposes in life. Simply existing is one of
the greatest gifts you can give someone you love and when you get down to
it, dismissing the mundane and confusing scientific aspects of nutrition, diet
and lifestyle are two of the most important facets of life that can give you as
well as others the gift of life. Be kind to yourself and never give up.
“You never fail until you stop trying.” – Albert Einstein
REFERENCES
1. Enos RT, Davis JM, Valazquez KT, et al. Influence of dietary saturated fat content on adiposity, macrophage behavior, inflammation, and metabolism: composition matters. Journal of Lipid Research. 2013; 54: 152-163. doi: 10.1194/jlr.M030700
2. Ludwig DS, Friedman MI. Increasing adiposity: consequence or cause of overeating?. JAMA. 2014; 311 (21): 2167-2168. doi:10.1001/jama.2014.4133.
3. Mozaffarian D, Hao T, Rimm EB, Willett WC, Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. The New England Journal of Medicine. 2011; 364 (25): 2392-2404. doi: 10.1056/NEJMoa1014296
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4. Nettleton JA, Jebb S, Riserus U, Koletzko B, Fleming J. Role of dietary fats in the prevention and treatment of the metabolic syndrome. Annals of Nutrition & Metabolism. 2014; 64: 167-178. doi: 10.1159/000363510.
5. Oliveira MC, Menezes-Garcia Z, Henriques MCC, et al. Acute and sustained inflammation and metabolic dysfunction induced by high refined carbohydrate-containing diet in mice. Obesity. 2013; 21 (9): E396–E406. doi: 10.1002/oby.20230/
6. U.S. and world population clock. United States Census Bureau. 2015; Available from: http://www.census.gov/popclock/