Fat. Hello my old friend.
We've had some good times together. Remember when I used to eat 2+ jars of peanut butter a week? Remember those 6 whole egg omelets with cheddar cheese? Remember the 3 tablespoons of olive oil drizzled over broccoli and chicken? Yeah, so do I.
If my examples are any clue, like many of you I thought dietary fat made you gain body fat. Like, it MADE you gain fat. Logically, it seems to fit; we eat something called fat and store something called fat on our bodies. How could it not make us gain bodyfat?
Later in life when I tried high fat diets, I did not see the results promised there either. I felt like Paleo diets, Ketogenic diets or other low-carb dogma were lying to me because I was eating tons of fat and not leaning out like they said I would. But the major misconception came from results that were sub par due to poor implementation.
I've learned quite a bit going from low calorie and low fat, to high fat and low carb, to high carb, high calorie and low fat back to somewhere in the middle. Combined with some time spent researching the physiology and metabolism of fat, carbohydrates, protein and their interactions, I'll tell you what you need to know.
Breaking Fat Down
What happens to fat in our bodies?
One of the mistakes we make when thinking about fuel sources for exercise is we are only concerned with what's in our blood stream. Since many of us have heard, and believe that carbohydrates make a quicker and more efficient fuel, that we need to eat them around exercise to have the best results.
This makes sense if you only pay attention to what you ate right before a workout. Sure, if you eat carbohydrates you can expect a level of blood sugar to rise 30-60 minutes after a meal (faster if its a simple sugar) which means we have more available fuel in our blood.
When you compare the simple transition of glucose into the bloodstream to dietary fat, this seems to strengthen the argument. If you eat carbohydrates, they are broken down into glucose and absorbed directly into the bloodstream from the small intestines. From there they can be stored in muscles, liver or fat cells.
Dietary fat has a longer road to your bloodstream. It must pass through ducts in the small intestine to the lymph tissue (a liquid tissue that collects dead cells, pathogens and bacteria) because it is too large to simply diffuse into the bloodstream through the intestinal wall like glucose does. The fat then circulates in the lymph until it is deposited into the blood from your left subclavian vein. From there it FINALLY can be picked up and used by tissues like muscles, liver and fat cells but we are talking some times 2-3 hours after eating.
So, this represents a much slower and less efficient fuel for direct activity. And, to compound that if the meal container lots of carbohydrates along with the fat and you used those carbohydrates for all your energy needs after the meal, then slow poke fat comes along 2-3 hours later, where does it go? Mostly fat cells.
Why you can't stop reading there
Here's why this isn't a death sentence for eating fat. Not all fat you eat goes right to fat cells. Just like glucose, when it's in your blood stream your muscles and other tissue have first dibs on grabbing it and either using it for energy or storing it for later. So yes, your muscles can store fat just like it can store glucose. But most importantly, your fat cells are constantly storing and breaking down energy throughout the day. So even in a calorie deficit, directly after a meal you might store some of that meal in fat cells but then break it down for energy BETWEEN meals when you aren't eating.
In this way, fat storage is kind of like the stock market. You store and burn fat all the time, it's the net result that matters! So at the end of the day, your fat loss or gain comes from whether you stored more than your burned or vice versa.
The beauty of dietary fat is that it makes a great fuel for anytime not engaged in intense exercise which for most of us, is about 23 hours out of our day. So even if you burn carbohydrates more intensely during a workout, you still have the rest of the day to contend with for energy - and fat does really well in this department.
What happens to fat during exercise?
God, if I could get one thing through people's heads it's that exercise presents a stimulus. That is what it's best for. It's good for telling your body, "hey, you should gain more muscle because you just had to lift this weight" or "hey, you should get more efficient at filling the heart and pumping blood because you just had to run for a while". Of course we use calories during exercise but that is not necessarily the main benefit. Our diet should determine ultimately if we are in a calorie deficit, maintenance or surplus. Our exercise should determine what we want our bodies to DO with those calories like build muscle, repair tissue, make more red blood cells etc.
Knowing this, we can stop obsessing about whether a workout is "fat burning". By fat burning you mean the fat on your body, not necessarily the fat in your diet. This is the misconception and we forget to differentiate the two. In fact, during exercise your body is using both fat and sugar for fuel but it's pulling those first from what is stored in the muscle (aha!) and will free up more sugar (glucose) from the liver and triglycerides from fat cells if the workout is long enough or demanding enough. But remember, YOU HAVE ENERGY STORED IN YOUR MUSCLES and that is where it comes from first.
So yeah, you store fat in fat cells but also in your muscle cells, which make it a convenient and readily used form of energy.
When do you use fat for fuel?
You're always using a mix of glucose and fat for energy, there's no way to "shut off" one system, it just comes down to what system is being called upon the most. At rest and lower intensity exercise like walking, jogging and circuit based training, fat makes up 50% of the fuel or more.
With exercise like this, you'll use stored fat (triglycerides) in the muscles. This works well because fat is readily broken down in the presence of oxygen which is why aerobic and less intense exercise uses it preferentially as a fuel. Once the muscles being worked cannot meet the demand of providing energy your body uses cortisol to mobilize body fat stores to provide triglycerides to be used as fuel.
But even during intense exercise like a set of squats, after using mostly stored muscle glycogen for fuel, during recovery between sets, you will shift back to using fat for fuel.
In this way, the body meets it's energy needs based on the task at hand. Even if you aren't using fat from muscles or fat cells directly during a specific exercise, you still use it between sets, during recovery and during lower intensity or even high rep exercises later in the workout.
Do you need carbohydrates around your workout, then?
You've heard time and again that you need carbohydrates for effective workouts and while table blood sugar is necessary for effective training, a lot of the carbohydrates you use during exercise are the ones already stored in your muscles. And studies have shown that even prolonged and intense exercise doesn't completely deplete the store muscle glycogen meaning that even moderate or low carbohydrate diets can provide enough energy for hard training. Some pre-workout carbohydrates like an apple, oatmeal or rice works well for energy because they help raise blood sugar which means there is more energy directly available as soon as you start exercising. However if you ate enough total carbohydrates AFTER your last training session, you should theoretically have enough stored glycogen in muscles to fuel that workout regardless.
One reason pre-workout carbohydrates help workout productivity is that the rise in blood sugar provides more fuel for the nervous system. However if you're healthy, the liver can manage this all on it's own. And again, if you ate enough carbohydrates AFTER your last training session, the liver will have enough stored glycogen too.
The only time taking in more carbohydrates around or during a workout is necessary is during prolonged exercise, 90-180 minutes or above, or during an event that has multiple sessions like an Ironman, Crossfit event or team sport. There's always the outliers who do really well with carbohydrates all the time but that isn't most of us.
The carbohydrate consensus
For the majority of us, we have plenty of stored glycogen in our muscle cells to use for energy (along with fat) during our workouts. The best time for carbohydrates, especially for fat loss, is in the meal directly after a workout. Not because it makes you gain more muscle but because it helps restore muscle glycogen for your NEXT workout. On top of that, you will more likely store all the carbohydrates in that meal in your muscles rather than fat cells during the post-workout hours which makes it again, a more convenient time to have them for fat loss.
Why fat can be your friend
Remember a second ago when I said the post-workout time was a great opportunity to have carbohydrates? That's because eating carbohydrates (and even protein) stimulates insulin. After a workout you need very little insulin to get those carbs in the muscle which is fantastic. But at other times, like when you had cereal for breakfast or pasta for lunch you need a lot more insulin to get the carbs into your muscle cell. Depending on the size of the meal and your sensitivity, this can be a big issue or no issue at all. But for those who experience rebound hypoglycemia or have issues with satiety, energy and mental clarity after big carb meals, it's an issue. And if you are overweight and need to lose fat, you can assume your response to carbohydrates is worse than someone who is lean.
In essence it might not even come down to total calories first as simply having you eat foods that give you sustained energy, mental clarity and keep cravings at bay helps a lot. In this case, dietary fats make a great choice because they are very satiating, don't stimulate insulin and provide a more sustained fuel.
The problem is necessarily that you eat carbohydrates and release insulin. That's normal and totally fine. It can be the chronic stimulating of insulin that causes your muscles to be less responsive to it creating a need for larger insulin spikes just to clear the glucose from your blood. Over time this means your muscles are less likely to accept nutrients and your fat cells will gladly take them. It also means if you DO get a response from your muscles, the insulin release might be so high that you get rebound hypoglycemia which is when your blood sugar drops too far below baseline, which creates some neurological issues. Ever get the shakes after eating something sugary?
So if we save most of our carbohydrates for post-workout when we barely even need insulin to store nutrients and eat more fat, protein and veggies at other times, we improve our insulin sensitivity. Which means when we DO eat carbohydrates they will not require a large insulin release and your muscles will preferentially take them up over fat cells.
We can't forget that dietary fat is essential (hence the name "essential fatty acids") for health. We literally have a lipid layer covering every single cell in our bodies. On top of that, we use the cholesterol our liver packages from fat to make hormones. How about estrogen, progesterone, testosterone and estradiol? All manufactured with a cholesterol backbone thanks to our good friend dietary fat.
Don't tell me you are going to get jacked and lean without testosterone for men or estrogen for women.
In fact, in men testosterone helps balance the effects of cortisol which can be a hormone that spurs further fat gain when chronically too high. In women, estrogen does the same. High cortisol can impact insulin sensitivity and even where you store body fat (like your midsection) so you do NOT want low levels of sex hormones due to very low dietary fat.
In terms of hunger and fullness, fat scores very high on the satiety index, meaning it helps make you feel satisfied after a meal as well as full between meals. It also really helps increase the palatability of vegetables and lean meats so you actually look forward to eating them. Nothing spruces up chicken breast like an avocado!
You also need fat to abdorb fat soluble vitamins like A, E and D. Vitamin D is a hormone that every single tissue in your body has receptors for, so you want optimal levels there as well.
Many fats like nuts and avocado contain fiber and minerals. Healthy oils like extra virgin olive oil, coconut oil and animal fats like butter provide antioxidants, fat soluble vitamins, minerals and things like CLA (conjugated linoleic acid) which has been shown to positively influence fat loss.
Summing up the fat game
The main take-away's:
1. Dietary and stored body fat make a good fuel source during lower intensity exercise as well as between sets of higher intensity exercise.
2. Body fat is THE primarily fuel source at rest.
3. Dietary fats do not stimulate insulin which can be helpful for steady energy and cognition levels as well as improved insulin sensitivity.
4. You do not necessarily need a ton of carbohydrates before or during exercise if you eat a well rounded post-workout meal of carbohydrates. You will have enough carbohydrates (and fat) stored IN THE MUSCLES to get you through the workout. Anything else will be stimulated by cortisol which will free up fat from fat cells and glucose from the liver.
5. Dietary fat is amazingly delicious, makes any food taste better and is highly satiating and filling.
6. Dietary contains cholesterol (in animal fats) or used to make cholesterol in the liver - this cholesterol is the building blocks of our hormone which have direct impacts on how well we burn fat and build muscle.
7. Dietary fat contains many beneficial nutrients like antioxidants, vitamins, minerals and micronutrients to help create a well-rounded diet.
How much fat?
For fat loss populations, somewhere around 40% of calories is a great starting place.
How do I figure this out?
For fat loss, 10-12 calories per lb is a great starting place. Here's some examples for 12 calories per lb:
120lbs x 12 = 1,440 calories x 40% = 576 fat calories / 9 calories per gram = 64g fat
140lbs x 12 = 1,680 calories x 40% = 672 fat calories / 9 calories per gram = 75g fat
160lbs x 12 = 1,920 calories x 40% = 768 fat calories / 9 calories per gram = 85g fat
As you can see, these numbers might be higher than what a lot of people are used to. Many clients, especially women, are eating 30-40g fat per day and constantly walking around hungry, cranky, craving and unsatisfied. If they dropped some carbohydrates and upped the fat, things would most likely improve.
Use a mix of quality nuts (no peanuts), olive oil, coconut oil, butter, avocado, animal fats like chicken thighs, beef and salmon and see how you feel. Your energy, cognition and workouts will feel much better.
Remember, fat is a misnomer. Let go of the word association and start embracing how powerful and healthy this food is.