1. 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 ofthe body,more specificallyin relationto foodand
metabolicfuels like glucose(carbohydrates),lipids(fats)and proteins. I’m acutelyaware of
how involved thehuman bodyis and how ambiguous and complexthe phrase“eat healthy”
can be.Everybody is different, from one’s childhood,lifestyle,anddailyresponsibilities(or lack
thereof)to how an individual’s bodymetabolizes,stores, and expends energy. It may be
difficult to appreciate that thesetwo central components of lifeare co-dependent;a person’s
dietarylifestylecan affect a person’s overalllifestyle and conversely, a person’s lifestylecan
affect a person’s dietarylifestyle. In an effort to help guidethemuddled path of balanced and
healthyeating andbetterequip any reader with the toolsto achieve one’s personal weight and
health goals,I’dliketo focus on and explainthree chiefaspects of nutrition that most people
are faced with on a dailybasis and thepotentialmetaboliceffectstheycan have on the human
body.Dietarysaturated fats (SFA), refined carbohydratesand overeating are three facets of
nutrition that are closelyinterrelated and “feed” off of one another.It’s typicalthat thesethree
categoriesare automaticallyandnegativelyassociated with what not to do or eat. I ask that
A

2. any person reading this willultimatelymake theirown educated decision on what they
consider to begoodor badfor themselves and theirown personal lifestyle.
SATURATED FATS
As most peopleknow, nation-wide and otherwise, theUnited Statesis experiencing its
highest levelof obesityrates ever recorded and, therefore, higherrates of acute and chronic
obesity-related diseases. MetabolicSyndrome(MetS), one
potentialcause of theaforementioned diseases, is defined as
high visceral adiposecomposition(abdominalobesity)in
conjunction with two of thefour following bloodlevels:high
bloodtriglycerides,high bloodpressure, high bloodglucose,or
a low high-densitylipoprotein(HDL)cholesterolratio to total
cholesterol(TC).4 Somehealth consequences ofMetS are theincreased risk of typeII diabetes,
cardiovascular disease (CVD), stroke and otherobesity-related diseases.4 Unfortunately,the
world-wide populationwith MetS is 25% which is currently on therise since “the prevalence of
MetS parallelstherising rates of obesity.”4 Thisstatistic represents one-fourth ofthe world –
that’sabout 1.8 billionpeople.6 Themost prevalent metabolicdysfunctionalcharacteristic
among thosewith MetS is insulin resistance (IR) which is even more prevalent in thosewith
MetS who also have high abdominalobesity.4 Insulin resistance is an unnatural physiological
disorder in which cells and tissues becomeless sensitive to the presence of insulin which in turn
inhibitsglucose from entering said cells and tissues. Over time, glucose willbegin to
accumulate in the bloodgiving rise to bloodglucoselevels which can significantlyincrease the
risk oftypeII diabetesas well as otherobesity-related diseases.

3. According to studies conducted by Susan Jebb,a professor of diet and populationhealth in
theUK, it was concluded that it is more effective to decrease energy consumption in order to
lose weight thanto adjust diet compositionin obese
peopleorthose with obesity-related health issues.4
With that being said, she also denotes in her findings
that since most overweight and obesepeoplewant to
lose weight as well as reduce theirhealth risks, it is
equally important to address fattyacidcompositionin
one’s diet.4 This acknowledgement leads me to the
controversial question asked byhealth professionals
and laymen, alike, are saturated fats actuallybadfor you?
In one research study on the relationship betweendietaryfattyacids and thedevelopment
of obesity,IR, and typeII diabetes,conducted byUlf Riserus, an associateprofessor of clinical
nutrition and metabolismin Sweden, it was found that in those with obesityand IR, excess free
fattyacids in thebloodwere unable to beabsorbed and converted into glucose or stored as
triglyceridesin theliver, skeletalmuscle or adiposetissue.4 This inabilityfor theliver, muscle
and fat tissue to absorbexcess free fattyacids for energy use or storage is what can leadto
increased risk of obesity-related diseases; thebodyisn’t ableto function normally and
therefore willreact abnormallyand possiblybecome diseased. Riserus also found in his studies
that therisk of diabeteswas inversely proportionateto adiet containing polyunsaturated fatty
acids (PUFAs) and vegetableoils, yet he also stated that “theeffects of different types of
dietaryfattyacids on obesityand fat accumulation have not been extensively investigated.” 4

4. One ongoing debatein thefieldof nutrition is the controversy between “good”and “bad”
fats and how much a person can consume of each beforehealth problemsarise. The research
for and against thissubject matter can get murky given there are several kinds offats and
several ways that theycan beused, stored, or transformed in thebody.The research on
saturated fats is difficult to analyze and conduct in human subjects; many research studies
state that theirfindings are inconsistent, contradictoryandinconclusive. For instance, one
study conducted on a panel of obesewomen
who were eitherinsulin-sensitive or insulin-
resistant, in which theywere eitherfed a high
carbohydrate[60% of totalenergyconsumed
(E)], low fat (20% E) diet or a low
carbohydrate(40%E), high fat (40%) diet,found that theinsulin-sensitive women who atethe
high carbohydratediet lost moreweight than theinsulin-sensitive women who ate thehigh fat
diet.Conversely, theinsulin-resistant women who ate thehigh fat diet lost more weight than
theinsulin-resistant women who ate thehigh carbohydratediet. Based on thisstudy, it can be
concluded that thestate of insulin sensitivity is a large factorin themetabolicrelationship
between weight loss and macronutrient distribution.4 One of themany suggested fat
substitutes for saturated fats are unsaturated fats (both poly-andmono-), however, “dataon
theeffect of increasing PUFA at theexpense ofSFA remain limitedand inconsistent.”4 It
seems that some research conducted on both animalsand humans suggests that PUFAs

5. improve weight loss, while otherstudies suggest increasing SFA compositionin thediet to
improve weight loss and health benefits. BertholdKeletzko,
a professor at theUniversity ofMunich MedicalCenter in
Germany, found that thosein western countries who
consume increased amounts of n-6 PUFA (vegetableoils)
and reduced amounts ofn-3 PUFA have an increased risk of
obesityand type2 diabetes.4
In a research study that was conducted to analyze themetaboliceffect of dietarysaturated
fat on subject’s fat compositionand accumulation, it was found, overall, that thosewho ate a
diet high in saturated fat (24%), as opposed to theaverage American diet saturated fat
composition(12%) and a diet lowin saturated fat (6%), yielded bettercholesterolpanels, less
fat accumulation, decreased insulin resistance, and an overall decreased risk for metabolic
dysfunction. The reasoning behindthis contradictorysupport for a high fat diet with 24% SFA
is that a diet this high insaturated fattyacids contains more medium-chain fattyacids (MCFA)
as opposed to long-chainfattyacids(LCFAs); MCFAs can transport from theintestines directly
to the liver for faster oxidationwhileLCFAs have to be transported through thebloodfirst
before theycan be stored and metabolized bythebody.Additionally,MCFAs are less likelyto
be stored as adiposetissue due to theirefficient oxidationcapabilitiesonceinside a cell.1
REFINED CARBOHYDRATES
There are two kinds of carbohydrates:simple and complex.Their names are definitiveof
how easilytheyare metabolized inthebody;simple (refined) carbohydratesare easilyoxidized
bythe bodywhilecomplex(unrefined) carbohydratesare oxidized at a slower rate. Being able

6. to absorb carbohydrateseasilyand faster may sound efficient and betterfor thebody,
however, thisis not thecase. Simple
carbohydratesare usually high on theglycemic
index while complexcarbohydratesare low; the
glycemicindex is a measure of how a foodwill
effect bloodglucoseand insulin levels. As blood
glucose increases, the release of insulin will
increase accordinglysince insulin is themechanism bywhich glucoseis ableto be absorbed
into cells to make ATP (energy). Overtime, if thereis enough glucose in theblood,thebody
begins to become resistant to insulin which means that glucosecan’t be absorbed into cells
and tissues for fuel and will, therefore,begin to accumulate in the bloodcausing rise in blood
glucose levels.
According to Ludwig, refined carbohydrateshave a negativeeffect on thebodyin that they
increase energy storage in fat cells which,as a result, decreases energy expenditureand
increases hunger. Additionally,sincethe fat cells absorb theenergy consumed, there isn’t
anything left to circulateor oxidize in thebodywhich leads thebodyto
believethat it’s hungry, possiblystarving, resulting in overeating.2 In other
words, thebodyabsorbs and utilizesrefined carbohydratefuelso quickly,
theirpresence as a metabolicfuel in thebloodstream is too short to
maintain a feeling ofcontentment after eating which leads to increased
hunger and foodintake.
One study that analyzed metabolicdysfunctionin mice as a result of high

7. refined carbohydrate-containing diets(HC)found that thosefed a HC diet exhibited “acuteand
sustained increase in visceral adiposity,glucoseintolerance,low insulin sensitivity [insulin
resistance] and hyperlipidemia[high bloodlipids]…”5 Withinthesamestudy, evidence showed
that even when foodintake and bodyweight were unchanged, themice on theHC diet hada
significant increase in theirvisceral adiposity(fat accumulationon vital organs).5 In another
study, obese young adults were put on eithera low fat diet or a low-glycemic-loaddiet
(indicativeof complexcarbohydrates).Results indicated that subjects on thelow-glycemic-
loaddiet lost more weight and experienced a decrease in percent bodyfat more so than those
on thelow-fat diet.Researchers deduced from thesefindings that “reducing the glycemicload
might beespeciallyimportant for achieving weight loss in individuals with high insulin
secretion.”4 Overall, this study supportsthe evidence that high-carbohydratecontaining diets
made up mostlyof refined carbohydrates(thosewith a high glycemicindex composition)can
drasticallyincrease fat tissue in the body(with orwithout weight gain) which is strongly
correlated with MetS.5
OVEREATING
There is a misconceptionunderstood to be true bysome peoplewho are trying to lose
weight that cutting calories is theanswer. This methodofweight loss can and is usually
successful in overweight and obesepeople,however, it is important to notethat an acute
decrease in availablefuel in thebodycan lead to extreme hunger and increased foodintake.2
This is why dieting isn’t as successful as making a dietarylifestylechange; peoplefeellimited
and cornered when only “allowed”to eat specific amounts of specific foods.On a psychological
level, people,evolutionarily andnaturally, start to resist and do theoppositeofwhat they’re

8. being told(even withinthemselves) when theyfeel liketheydo not have choiceor control in a
situation; thisstands true when peopleaddresstheir dietaryhabitsand composition.People
need to have choice and control over theireating to be
successful in the long-run. When peopledeprivethemselves
of food or specific kinds of foods,both a psychologicaland
physiologicaleffect canoccur leading to psychological
resistance as well as a strong physiologicaldriveto eat,
which usually leadsto indulgences and overeating.
On a biologicalandchemicallevel, without needing to know theexact chemical structures of
carbohydrates,fats or proteins, or thebiologicalchemicalreactionsthat can occur with or
between these macronutrients, thebodyis capableof breaking down and absorbing
carbohydrateseasier than fats or proteins. This means that when a person eats, the
carbohydratesconsumed will be broken down and used up as ATP (energy) first before fat or
proteinwill be. In thecase of overeating, thebodycan only breakdown, absorband utilize a
certain amount of foodbefore it reaches itsthreshold.When this thresholdis met, thebody
will store any excess and unnecessary energy for later use which means fat willbe utilized
secondarily, if at all, resulting in fat accumulation throughout thebody.As a note, proteinisn’t
our focus in this analysis of macronutrient oxidationandstoragebecause it is thethirdand last
macronutrient to be used as fuel bythe body.
In a studypublished in The New EnglandJournal of Medicine, researching theeffects diet
and lifestylecan have on long-term weight gain,it was suggested that “dietaryquality (the
typesof foods and beverages consumed) influences dietaryquantity(totalcalories).”3 These

9. findings were further supported by thepositivecorrelationobserved between increased
consumption of starches and refined carbohydrateswith weight gain.3 Ultimately,with
overeating, it’simportant to consider both thediet composition,mostlyfocusing on dietary
fats and carbohydratesconsumed, as well as theamount of energy consumed as to not
consume more energy thanexpended on a dailybasis.
FOOD FOR THOUGHT
The bodyis a tricky,messy, intricate web of chemicaland
biologicalreactionsthat aremeant to keep everything in balanceto
keep us healthyandalive, however, as we’ve learned, our part in
thisequation is not that simple.We, as humans, are perfectly
imperfect and it is our duty,to thebest of our abilities,to feed our
bodiesappropriatelyso that we can continue living on in thisworld
and fulfill our individualpurposes in life. Simplyexisting is one of thegreatest gifts you can give
someone you love and when you get down to it, dismissing themundane and confusing
scientific aspects of nutrition, diet and lifestyleare two of themost important facets of life that
can giveyou as well as others thegift of life. Bekind to yourself and never give up.
“Younever fail untilyoustop trying.” –Albert Einstein

10. REFERENCES
1. Enos RT, Davis JM, Valazquez KT, et al. Influence of dietarysaturated fat content on
adiposity,macrophagebehavior,inflammation,and metabolism:compositionmatters.
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 lifestyleand
long-term weight gainin women and men. The New England Journal of Medicine. 2011;
364 (25): 2392-2404. doi:10.1056/NEJMoa1014296
4. NettletonJA, Jebb S, Riserus U, Koletzko B,Fleming J. Role of dietaryfats 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 metabolicdysfunctioninduced by high refined carbohydrate-
containing diet in mice. Obesity. 2013; 21 (9): E396–E406. doi:10.1002/oby.20230/
6. U.S. and world populationclock.United States Census Bureau. 2015; Availablefrom:
http://www.census.gov/popclock/