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How Does The Body Convert Food Into Fat? | Nutritionist Explains | Myprotein
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Jan 30, 2025
Expert nutritionist explains how the food you eat gets transformed into the fat you store in your body. In this video, we’re going to take an in-depth look at how the food you eat gets transformed into the fat you store on your body and how that builds up over time. Dr Richie Kirwan answers some important questions like, do all carbs get turned into fat immediately? And if you’re on a low-carb diet and your insulin is low, does that mean you won’t store any of the fat you eat? There are a few different factors involved in how we store body fat, and Richie is going to do a deep dive into all these factors so you have a better understanding of why body fat storage happens. *** Chapters: 00:00 - Introduction 00:51 - Carbohydrates 04:13 - Protein 05:15 - Fats 06:16 - Energy balance 07:40 - Body fat storage 10:08 - Any more questions? *********************************
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0:00
how does a donut turn into love handles
0:02
let's talk about
0:03
[Music]
0:06
that how's it going guys my name's
0:08
Richie Kerwin and if you've ever
0:09
wondered how you end up wearing that
0:12
delicious meal you've just enjoyed well
0:13
you're in luck because today we're going
0:15
to take an in-depth look at how the food
0:18
you eat gets transformed into the fat
0:20
you store on your body and how that
0:22
builds up over time we'll also answer
0:24
some important questions like do all
0:25
carbs get turned into fat immediately
0:27
and if you're on a low carb diet and
0:29
your insulin is low so does that mean
0:31
you won't store any of that fat you eat
0:33
now there are a few different factors
0:35
involved in how we store body fat and
0:36
we're going to talk about these factors
0:37
so you have a better understanding of
0:39
why body fat storage happens to help
0:41
with that I'm going to use a good old
0:43
burger and a fizzy drink to break down
0:45
what happens to carbohydrates proteins
0:47
and fats in your body after a meal let's
0:50
start with carbs which are going to make
0:52
up the vast majority of the calories in
0:54
the burger bun and pretty much all of
0:55
the calories in the sugary drink when
0:57
you eat starch a type of complex
0:59
carbohyd hydrate starts getting broken
1:01
down by amalay an enzyme in your saliva
1:03
carbs also get broken down by similar
1:05
enzymes in your small intestine just
1:07
after your stomach starch and any other
1:09
carbohydrates like sugar get broken down
1:11
into simple sugars of which there are
1:13
three types glucose fructose and
1:15
galactose glucose gets absorbed through
1:17
the wall of your digestive system into
1:18
your bloodstream and gets transported
1:20
all around your body this is because
1:22
glucose is one of your body's primary
1:23
energy sources along with fatty acids
1:25
which we'll talk about in a little bit
1:27
fructose gets absorbed directly to a
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vein called the p and gets delivered
1:31
directly to the liver where it can be
1:32
used as energy and if it's not needed
1:34
for energy it gets converted into fat
1:36
we'll talk about how that happens in a
1:38
moment now when you eat most
1:39
carbohydrates like I said glucose gets
1:41
released into your blood and your blood
1:42
glucose levels go up the problem is your
1:44
body likes to keep the amount of glucose
1:45
in your blood nice and stable so if your
1:47
blood glucose gets too high body will
1:49
release a hormone called insulin which
1:51
brings your blood glucose back down
1:52
before I go any further it's really
1:54
important to say that if you're healthy
1:56
you don't need to worry about your blood
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glucose Rising after meal that's
1:59
completely normal and as long as you're
2:01
healthy your body can bring that glucose
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down to normal levels quite quickly
2:05
spikes in blood sugar are supposed to
2:07
happen when you eat carbs and it's only
2:09
a problem if you're metabolically
2:10
unhealthy and can't bring the glucose
2:12
level back down quickly enough now like
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I said insulin's job is to lower blood
2:16
glucose and it does that in a number of
2:18
ways firstly it increases the burning of
2:20
glucose for energy and it reduces the
2:22
burning of fat to get your body using
2:24
all that excess glucose floating around
2:26
in your blood system then it also causes
2:28
your body to store more carbohy to get
2:30
glucose out of circulation the liver and
2:32
your muscles can convert some of the
2:34
excess glucose into glycogen for storage
2:36
glycogen is a polysaccharide made up of
2:38
loads of glucose molecules stuck
2:40
together as chains when we need energy
2:41
later for activity we can break down
2:43
that glycogen into glucose again the
2:45
average athletic male for example who
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weighs about 70 kg has about 600 G of
2:50
glycogen stored in their muscles and
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liver the more active you are the more
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glycogen you can store which is one of
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the reasons being physically active and
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having plenty of muscle is good for
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blood sugar control now if your muscle
3:01
glycogen stores are full and if you
3:03
don't need to use the extra glucose in
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your body straight away for energy your
3:07
body still needs to get rid of it
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somehow and it does that by a process
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called denovo lipogenesis that's just a
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fancy way of saying that your body
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converts glucose or any carbohydrate
3:16
like substance into fatty acids those
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fatty acids get transported in your
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blood to adipocytes a fancy name for fat
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cells once inside the fat cell the fatty
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acids combin with a molecule of glycerol
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to form a triglyceride otherwise known
3:30
as fat your fat stores are an amazingly
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efficient way of storing energy in a
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small space and an average 70 kg person
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with about 15% body fat or 10 kg of body
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fat Mass has about 990,000 calories of
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stored energy now here's something
3:44
really important to understand about
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denovo lipogenesis it's not a very
3:48
efficient process in fact as much as
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almost 25 to 30% of the energy contained
3:53
in carbohydrate can be lost in all
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enzymatic processes that turn it into
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fat that means storage of fat from carbs
4:00
is only 70 to 75% efficient and because
4:03
of that the body is more likely to burn
4:05
carbs for energy straight away than
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store them as fat under normal
4:08
conditions now let's move on to the meat
4:10
in the burger and importantly the
4:11
protein protein digestion begins in the
4:13
stomach with an enzyme called pepsin and
4:15
continues in the small intestine where
4:17
other enzymes break that protein down
4:19
into amino acids these get absorbed in
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the small intestine and transported in
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the blood around the body normally amino
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acids are used for protein synthesis
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like building muscle and other important
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functions like hormones and enzymes
4:31
however during times of excess protein
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intake or low energy needs amino acids
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can be converted into glucose through
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glucon neogenesis this means that the
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nitrogen containing amino groups are
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removed from the amino acid in a process
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called deamination the amino group is
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eventually converted to Ura which we pee
4:48
out in our urine and the rest of the
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amino acid is converted into glucose
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which we can use for energy if there is
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still an excess of glucose beyond what
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your body needs for energy it can be
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converted into fat through denova Li
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Genesis just like I explained for carbs
5:01
but under normal conditions as in
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someone isn't eating way more energy
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than they need over a long time we don't
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convert much protein into body fat at
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all far less than carbs time to talk
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about the last macronutrient in that
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burger fat the fat would be found mostly
5:15
in the burger patty itself and once you
5:17
eat it the fats are broken down into
5:19
fatty acids and glycerol in the small
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intestine by enzymes called lipases from
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the small intestine fatty acids get
5:24
absorbed into the intestinal cells where
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they recombine to form triglycerides a
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fat molecu again now because fat doesn't
5:30
mix well with blood those triglycerides
5:33
get packaged into little particles of
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fat called kyom microns which are
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similar to the particles that transport
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cholesterol around the body those kyom
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microns don't get released directly into
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the blood and instead are released into
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the lymphatic system which is a whole
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other network of vessels in your body
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from there the kyom microns eventually
5:50
enter the bloodstream Once In The Blood
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the kyom microns can supply cells around
5:54
your body with fatty acids which are a
5:56
valuable source of energy however if
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your body doesn't need the energy right
6:00
then and there it has to get those
6:01
excess fat particles out of circulation
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and it does that by sending them to fat
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cells for storage remember when I said
6:07
that the conversion of carbs to Fat was
6:08
only 70 to 75% efficient so the body
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doesn't do it that much under normal
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conditions of energy balance well
6:14
converting the fat you eat to store body
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fat is about 98 to 99% efficient yep you
6:20
heard right it is incredibly easy for
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your body to store dietary fat as body
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fat now does that mean that eating fat
6:27
makes you fat and eating carbs doesn't
6:29
no that is not what I'm saying you see
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what we haven't really spoken about here
6:33
is energy balance or how much energy
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you're eating compared to how much
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you're burning if you're eating just
6:38
enough calories to meet your energy
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needs over the long term you won't store
6:42
any extra body fat that doesn't mean you
6:44
won't store any body fat you will and in
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fact we are more or less continuously
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storing and breaking down body fat over
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the course of the day that's why it's
6:51
calorie balance in the long term that
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makes a difference to whether you gain
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or lose body fat so if you eat more
6:57
energy than you need to burn over the
6:59
long term whether it's fats or carbs
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you'll end up storing more body fat if
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you're eating a diet with normal levels
7:05
of fat carbs you'll just store more of
7:07
the fat you eat because your body tries
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to burn more carbs when you eat them but
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it can convert excess carbs to fat too
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if you eat enough and to clarify the
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single biggest determinant of whether
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you'll store body fat or not is the
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total amount of calories you eat if you
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eat more than you need for long enough
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you'll be adding more body fat now there
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are a few other interesting points about
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body fat that are worth mentioning I've
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mentioned in a previous video on why
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it's so easy to gain weight that the
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human body is incredibly efficient at
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storing body fat and if you eat enough
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your body fat stores can just keep
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growing theoretically indefinitely fat
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cells can either increase their size a
7:41
lot in a process called hypertrophy
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which is much more likely when we
7:45
overeat or they increase the number of
7:47
fat cells in a process called
7:49
hyperplasia this process is called
7:51
atopos tissue expansion and means that
7:53
body fat stores just keep getting bigger
7:55
now your body prefers that most of the
7:57
fat is stored under the skin which which
7:59
is called subcutaneous adapost tissue
8:01
but after a certain point of body fat
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gain your subcutaneous fat stores start
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to reach their limit and body fat starts
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getting stored ectopically which means
8:09
it gets stored in places you don't want
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it to such as visceral adapost tissue
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around your organs in your liver and
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even inside your muscles when body fat
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starts getting stored ectopically like
8:18
this is when a lot of health problems
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associated with excess body fat start to
8:22
happen such as insulin resistance fatty
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liver and increases in chronic
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inflammation the thing is everyone seems
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to have a different point at which they
8:30
start storing body fat ectopically so
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some people can gain a lot of body fat
8:34
without any health issues initially
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While others might start having problems
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at relatively lower levels of body fat
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this is called the personal fat
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threshold and it's studied a lot in
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research around insulin resistance and
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diabetes now just before we finish up I
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want to touch on another common myth
8:48
about fat storage I already mentioned
8:50
that insulin is an important storage
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hormone when you eat carbs or protein
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your body produces insulin which
8:54
increases the burning of glucose for
8:56
fuel reduces the burning of fat for fuel
8:58
and promotes the storage of of carbs and
9:00
fat hearing that might make you think
9:01
that insulin causes people to gain
9:04
weight and completely stops fat loss but
9:06
you'd be wrong the thing is insulin only
9:08
has those effects when its levels are
9:10
elevated and insulin is only high or
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elevated for a short time after you eat
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at least in healthy people so after a
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couple of hours your body goes back to
9:18
its normal state which includes burning
9:21
fat which it can take out of your body
9:23
fat stores and don't forget we usually
9:24
spend a lot of the day not eating food
9:26
including those 8 hours at night that
9:28
you should be sleeping which gives your
9:29
body plenty of time to use all that
9:31
stored body fat there have been plenty
9:33
of experiments that have shown that
9:34
weight loss is still possible when
9:36
people eat diets that increase insulin
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secretion such as the famous rice diet
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of the 1940s and 50s with over 90% of
9:42
the diet's calories coming from
9:43
carbohydrates even in a study of high
9:45
carb plant-based diets versus low carb
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keto diets despite the fact that the
9:50
high carb diet led to higher glucose and
9:52
insulin levels people still lost more
9:54
weight than the keto diet because they
9:56
ended up eating fewer calories and at
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the end of the the day when it comes to
10:00
Fat storage what matters most is how
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many calories you eat and don't let
10:05
anyone try to convince you otherwise so
10:08
we've covered a lot about how your body
10:09
stores body fat after you eat and I
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really hope it's helped clear up any
10:13
myths you might have heard about it as
10:14
always if you have any more questions
10:16
let me know in the comments below and
10:17
remember to like And subscribe to my
10:19
protein YouTube channel for more great
10:21
evidence-based nutrition
10:26
information
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