The Real Skinny on Low Carb Diets – A Critique.

March 6, 2016
Feng-Yuan Liu

This is a Critique of “The Skinny on Low Carb Diets” by Jenelle Croatto. The original article found here: https://www.12wbt.com/blog/nutrition/the-skinny-on-low-carb-diets/

Before I start, I want to preface this by saying that this article is not intended to “carb-shame”, but rather present the facts, which unfortunately is so often neglected when writing about carbohydrates and diet.

 

DEFINING THE UNDEFINED

So often we hear of the term “Low-Carb” – low carb bars, low-carb breakfast cereals, low-carb pastas, low-carb diets….so, my first question is: what exactly is LOW carb?

Unfortunately, in Australia and around the world, there is no clear definition. One source will claim that the MINIMUM we should consume a day is 130g of carbohydrates (hence implying that anything below that is technically low carb). Another source will state that low carb is less than 20% daily intake (which for someone on a 2000kcal a day diet means 100g of carb versus for someone on a 1300kcal a day diet means 65g of carb). The most extreme sources I have come across suggest 10% of total daily energy from carbs (which using the above example of 2000kcal and 1300kcal a day means 50g and 30g respectively of carbs). For the sake of this article, I am going to adopt a somewhat middle ground and say 50-65g of carb a day is “Low Carb”

However, I am yet to come across a single source that suggest we eat ZERO carbs. So the first point I want to make is: when we are talking low carb, a) the definition varies dramatically, and b) we do NOT imply no carbs.

 

WHY WE DON’T NEED CARBS

  1. It is not a premium energy source, nor is it the only energy source

Our body uses carbs as the first line of energy because it is readily available and accessible. In a modern Western diet, carbohydrates are very abundant, so the body adapts to using exogenous glucose from carbohydrate foods as fuel. So – what happens when we don’t have much carbs in our diet? Our body can produce glucose endogenously via gluconeogenesis, a process whereby the body creates glucose using non-carbohydrate derivatives such as amino acids (from proteins) and lipids (from fats). The body can also produce ketones for energy, running the body on fat as fuel as opposed to glucose as fuel.

 

  1. It does not help with sugar cravings

When our body is running on fats as fuel, insulin and blood glucose levels are low and stable, hence eliminating the normal issues with sugar cravings, post prandial slumps and strange energy spikes and dips throughout the day. Also a diet high in protein and healthy fats are much more satiating anyway! Who has ever had eggs for breakfast and noticed they don’t feel the need to snack mid morning?

 

  1. It is not involved in fat burning, let alone optimises fat burning

One thing I want to clear up before proceeding is: reducing carbs does NOT mean necessarily reducing total calories. Reducing carbs simply means reducing the quantity of carbs, but one can still increase fats and proteins for energy and satiety.

Now, in contrast to this unreferenced “population study” that apparently shows that those who include wholegrains in their diets tend to have smaller waistlines and be leaner, I have a referenced study that shows the striking contrast in FAT loss for those on a low-carb diet, versus a low-fat diet. Furthermore, this study also showed improvements in risk levels for heart disease in the low-carb group versus the low-fat group (Bazzano, LA, et al. Effects of low-carbohydrate and low-fat diets: a randomized trial. Ann Intern Med. 2014 Sep 2;161(5):309-18.). So – do carbs optimize fat burning? Apparently not.

As for the sensationalist journalism used to compare “soft white bread” to “steak” when describing their “eatability versus satiability” – I don’t think I really need to comment here.

 

A FINAL NOTE ON FIBRE

I believe that fibre is very important for bowel health. I also believe that fibre does not require eating pasta to obtain (100g of cooked pasta only giving us 2g of fibre) which is no more than what 100g of green beans, carrots, broccoli or eggplant would provide (100g of each would give you 2-3g of fibre). In a day, we are recommended 30g of fibre – so the question is: can we meet this on a “low-carb” diet (remember, we are using 50-65g carb a day as a guide)? Let’s find out:

 

Food Quantity Net carb Fibre
Raspberries 50g 2.5g 4g
Chia seeds 1 tbsp 1g 3g
Green beans (as an example) 200g 7g 7g
Black rice 125g cooked 26g 4g
Psyllium husk 1 tbsp 0g 10g
TOTAL 36.5g 28g

 

The answer is: Yes.

 

The Bottom Line?

I am not writing this to advocate carbs one way or another for the general population. I am simply presenting facts and figures, and obviously, disagreeing with the general tone of the original article I am critiquing.

As dietitians we are there to educate and present our clients with facts so they can decide whether a low carb approach is for them or not. We should not form pre-conceived stances on these things and attempt to sway our clients one way or another based on our own beliefs.