Eat Your Carbs With Your Fats

by Dean McKillop 3574 views Nutrition

Eat Your Carbs With Your Fats

I thought this was a thing of the past but it appears to still be a question left unanswered. Can you eat or should you eat carbohydrates and fats together?

The theory goes

Eating high carbohydrates, which results in the release of insulin, alongside high dietary fat intake, results in an increase in fat storage due to the coupling of high insulin alongside high circulatory triglycerides. It sounds feasible in theory, albeit a very simple theory, but the reality is, it misses some fundamental considerations of fat gain, fat loss and whether or not the net loss of fat/weight at the end of the day is either positive or negative.

Let me put it a different way.

Say I have a petrol tank that holds 50L of fuel that is currently half full at 25L. I take my car out and I drive it for 3 hours, burning 20L of fuel and then on my way home I stop and put 20L back into my fuel tank. The end result upon returning home, is a fuel tank with 25L in it… the same as what I left with.

Conversely, let’s say I have the same fuel tank at 25L and I drive it for 1hour, burn 10L and then fill it back up 5L. I drive another 2 hours, burning a further 15L and then on my way home I fill it up with 20L of fuel just before I arrive home. In this scenario I have burned the same 20L of fuel, however I have refilled the tank twice, and yet I arrive back home with the same sized fuel tank, filled to the same level.

In these scenarios, your body’s fat cells are your tank and the food you eat is the fuel. Regardless of whether you fill those fat cells up once, twice, three times or even 10x in the day, provided the fuel intake matches the fuel output, you will finish on the same net gain, loss or maintenance of stored energy.

Which is where the concept of eating your carbs and fats separately fails.

It completely ignores the energy balance equation and focuses solely on the insulin hypothesis, whereby Insulin is blamed as the primary culprit for fat storage and weight gain, irrespective of calorie consumption. The other thing the insulin theory fails to acknowledge completely is that carbohydrates are not the only insulinogenic food you can consume (1).

In fact, some proteins such as whey or free form amino acids rank high on an insulinogenic scale, which would then imply protein and fats should also be kept separate based on this hypothesis of insulin causing fat gain.

Yet we hear the complete opposite to this, whereby fitness professionals promote protein and fats together throughout the day based around the theory of improving insulin sensitivity, while completely ignoring the insulinogenic effect of proteins.

The reality is this

Insulin is an anabolic hormone, it does impede lipolysis (breakdown of fats) while in circulation and it is responsible for the storage of fatty acids, carbohydrates AND amino acids. However, it does all of this on a consistent daily basis like an off on switch. Insulin and its effect on body composition is a multifaceted hormone, whereby its effects are cyclical based on its requirements.

What insulin isn’t though, is the hierarchy of fat storage.

carbs and fats

By reducing caloric intake, which traditionally comes from both carbohydrates and fats, you simultaneously reduce the net insulin effect on the body over the course of a day. Whether you consume your daily intake of carbohydrates in 1, 2 or 5 meals, provided the total carbohydrate amount consumed remains constant, the insulin load will in essence be the same or at least very similar.

The storage capacity at the end of the day remains the same and in essence, fat storage, loss or maintenance is controlled by total caloric and total macronutrient intake, not time specificity of intake (2) and certainly not whether or not certain macronutrients are consumed together.

Regardless of this, lets entertain the logicality of separating macronutrients for a second.

Let’s just say you eat 10g of fat and store it as a sub cutaneous triglyceride when eaten alongside a carbohydrate. But then for the rest of the day you separate your carbs and fats yet you still eat in a total daily caloric deficit (less than your burn). The reality is, when you eat in a deficit of calories, your body increases lipolysis (the breakdown of fat) in order to provide usable energy for daily activities.

Regardless of whether the 10g of fat you consumed with carbohydrates is stored, the major concern when looking at body composition is whether or not your net fat breakdown is greater than your net fat storage, which is determined firstly by caloric intake and secondly by daily macronutrient distribution.

Fat storage is not determined by nutrient timing!

So you store 10g of fat due to consuming it alongside carbohydrates, yet you burn 15g of stored triglycerides in the day due to the deficit of calories you are in.

The calorie deficit negates the theoretical increase in fatty acid storage.

While theories sometimes sound good, the reality is that our body is not a simple system that works on absolutes. If we could so simply manipulate its storage, breakdown and utilisation of nutrients by changing something as quick as macronutrient content of a meal, we wouldn’t have the multi billion-dollar health industry of today trying to help people lose body fat.

Similarly, if carbohydrates were really the problem and consequently insulin too, that would mean you couldn’t gain fat on a ketogenic diet either.

Which is also a falsity, as you can gain fat on a ketogenic diet even though the presence of insulin is far lower than it would be in a traditionally higher carbohydrate diet.

So as always with my articles I will end with this…

Reduce dietary confusion, always consider the context of a claim and find dietary balance if you want to achieve long-term success.

Nutrient timing is not the answer to solving fat loss physiologically. 

Bell, Kristine. (2014). Clinical application of the food insulin index to diabetes mellitus. Thesis: The University of Sydney.

Golay, A. et al. (2000). Similar weight loss with low-energy food combining or balanced diets. International Journal of obesity and related metabolic disorders. 24(4) pp 492.496.


Dean McKillop

Exercise Scientist

I completed my Exercise Science Degree at the University of QLD and have worked in the fitness industry for over 8 years, including a short stint at the Brisbane Broncos in 2010 as a student. I also hold my Level 2 Strength and Conditioning Coach accreditation (ASCA) and have competed in 1 bodybuilding season, placing 2nd at the IFBB u85kg Nationals.

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