Yes, carbs are still getting a bad name and there are still too many people under the belief that the way to fat loss is to reduce/ remove carbohydrates from their diet.
So why is this? Why do we think that in order to lose fat we have to remove the carb & that carbs are the enemy?
Carbs bad/fats good?
Now that ‘fat is not the enemy’ & has become widely recognised due to the research on healthy fats in the diet equating to improvements in hormonal health & general health overall it seems we have to make another food group the enemy.
We now know thanks to research by Ingram et al (1) and such-like that the inclusion of fats within the diet is vital especially in females where it is responsible for the production of pregmanalone which is required for conception.
We are also much more aware of the importance of protein in our diet & especially when it comes to improving body composition. Thus carbohydrates have become the popular variable.
The low carb diet = fat loss exists because people think that:
- Carbs are the only macronutrient that is not essential therefore we don’t need any
- Carbs are well known for the production of insulin which is required to carry the glycogen into cells alongside a certain amount of water thus resulting in intra cellular water
- Carbs can cause inflammation especially in grain types
Anyone who has tried a low carb diet will most probably have initially lost weight and appeared leaner due to an overall reduction in caloric intake coupled with less intra cellular water.
However, is a low carb diet a long term solution?
The answer is usually no.
Are some foods just bad?
Like any diet (think Atkins, gluten free, 5:2) embarked upon for a short duration, initial weight loss will occur mostly due to the exclusion of an entire food group (unless you are actively replacing this) and in a low carb instance some of this will be attributed to lowered water and glycogen levels.
These diets are all examples of one key factor. Calorie restriction, whether you are cutting out carbs, fasting for most of the day or removing gluten grains you are cutting out a source of calories. The fact of the matter is that 24-hour energy balance is the variable you need to be looking at and so long as you are in an energy deficit you will lose weight. Cutting out certain food groups or fasting are just methods for creating that deficit.
However, done extensively, this can lead to extensive hormone disruption such as elevated cortisol levels, decreased testosterone production and reduction in thyroid production, all of which are the opposite of what is required for optimal body compositional changes (2).
So what does all this mean?
Let’s look at them one at time:
An elevation of cortisol levels means increased inflammation resulting in the inability to lose weight. Higher cortisol levels are synonymous with carrying extra fat around the torso in females.
Reduction in testosterone output means less ability to gain lean muscle tissue. Lean muscle tissue as we know, is anabolic and extremely important when it comes to increasing metabolism. An increased metabolism means a higher basal metabolic rate, the rate at which your body burns calories at rest. So in effect, good levels of testosterone = ability to build lean tissue= higher metabolism.
The reduction of carbohydrates in the diet can lead to a decrease in your body’s production of the hormone T3 which regulates the metabolism and blood glucose.
Not only that, but a low carb diet can increase the output of the Reverse T3 hormone which inhibits T3. Now remembering that the aim in a fat loss goal is to keep the metabolism as high as possible doesn’t it make sense to retain healthy T3 markers?
(Let me stress at this point that what I am referring to in this blog is about fat loss but not in overly obese individuals who may have levels of insulin resistance and, in which case, need to be addressed by an RD.)
Long term adherence to a low carb diet can result in stress hormones rising, the inability to build lean muscle tissue and a slower metabolism. Not optimal in the quest for fat loss. Definitely NOT what females want in order to sustain long term fat loss.
Not only that but in females, long term damage to these hormones can result in menstrual cycle and fertility problems.
What about the role of carbohydrates in training?
Compliance with any weight loss program is the most important factor for success.
Fuel your training
Everyone will probably know of that person who is on a ketogenic diet and feels ‘amazing’. That person (if actually in ketosis) will be a rarity as it’s much harder to be in ketosis than people assume. There are studies shown where certain athletes perform better on a low carb diet however this is a small minority. There are also individual cases in which people with specific medical conditions could fair better such as those with epilepsy or diabetes but medical advice is advisable in such cases.
Carbs are the body’s preferred source of fuel, vital for brain function and required for fuelling exercise. The preferred fuel source for both the muscular and nervous systems. Anyone partaking in vigorous forms of training will essentially function more optimally with a decent level of carbohydrate in their diet. This has been researched and proven extensively by the likes of Prof Graeme Close at St Johns Liverpool University (3) who has spent many years working and researching various athletes.
As training output is an important marker when we are considering fat loss- in order to get the most out of our training sessions we need to be able to train with intensity.
When you are on in a calorie deficit there is always going to be a limited number of carbs in your diet as carbs and fats most commonly become the variable. One way in which to utilise these is to eat your starchy carb sources in the meals around your workouts as we want to ensure that the carbs we are eating are going to the places we want them to get to. These are times when carbs are metabolised the best.
Before your training session you want glycogen stores topped up and get glucose into your bloodstream so you have energy to train.
During your session they can be used to minimise muscular breakdown, increase training intensity and feed muscular swelling.
Post training is when we need them the most in any time of the day for quicker and effective glycogen replenishment. Research has also shown that carbs and protein together are more efficient for protein synthesis than just protein alone.
So, therefore being in an anabolic state in and around your training sessions makes sense when you are aiming to at the very least preserve lean tissue.
In summary, low carb diets like any can result in short term fat loss but are not an advisable long term solution as in any overly restricted diet. This is especially prevalent in females due to the delicate hormone balance.
Compliance with any weight loss program is the most important factor for success above all therefore monitoring the number of carbs in your diet as well as their timing in meals will be better than removing them. While the composition of one’s diet is important essentially the calories in/ calories out equation still holds true- so instead of getting on the ‘low carb’ band wagon- assess your overall intake/ output equation, have a balanced diet and use the carbs in your diet to fuel your training.
The science behind fat loss, nutrient manipulation and energy balance is all covered extensively on the BTN Practical Academy. If you're a trainer, coach or athlete you can sign up here.
- Ingram DM, Bennett FC, Willcox D, de Klerk N. Effect of low-fat diet on female sex hormone levels. J Natl Cancer Inst
- The role of T3 and its receptor in efficient metabolisers receiving very-low-calorie diets Moore R, Mehrishi JN, Verdoorn C, Mills IH
- Effects of dietary carbohydrate on delayed onset muscle soreness and reactive oxygen species after contraction induced muscle damage. Close GL1, Ashton T, Cable T, Doran D, Noyes C, McArdle F, MacLaren DP