top of page

High Carb Vs Low Carb - Which is better for fat loss?

Despite being no new thing, the low carb revolution is building momentum with keto advocates haling its approach as the holy grail of weight loss, performance, mental aptitude and even an elixir for longer life…. So should we take note? Are they on to something, is this simple strategy of swapping popcorn for bacon really going to make a difference?

OK but why would you go low carb? (Seriously, why would you want to give up chocolate?)

The insulin hormone hypothesis

The main rationale behind why carbs are the enemy is that the hormone insulin prevents lipolysis, or the release of fat from your fat cells. It also increases the amount of fat taken up by these fat cells. Not good right?!

So with this logic the argument goes cut carbs completely, add cinnamon to anything and everything (I was once guilty) and NEVER have sugar by itself, otherwise your world will come crashing down and you’ll get fat, really fat.

Damn you insulin.

Hang on hang on, it may not be that simple.

There’s a few issues with this debate.

1. It’s not just carbohydrates that stimulate insulin

Protein is insulinemic too, yep it also spikes insulin and when combined with carbs it actually produces a greater spike than carbohydrates alone (1), yet we know now a high (relative) protein/moderate carb diet is effective in improving body composition (2, 3).

Even in obese subjects (I’ll come on to this later), a study (4), albeit small showed that a higher protein diet still elicited better weight loss, despite curbing metabolic benefits (reducing insulin sensitivity). Highlighting how higher insulin levels don’t necessarily affect weight loss.

2. Fatty acid release does not mean fat loss

Just by blocking insulin and enabling fatty acids to leave the cells does NOT necessarily equate to a loss in body fat, as many of these fatty acids actually go back into the fat cells (re-esterification).

What?? Yep, really, fat flux or how fatty acids leave and enter the cells is actually a continuous process that goes on throughout the day. So even when insulin is kept low, the majority of theses fatty acids are popped right back as they’re not needed (we store fat for energy after all). It’s only when we have a big enough energy demand that they go through another process called beta-oxidation where they are finally used.

So you have to be in an overall energy deficit (if you don’t know about energy balance then check out this post) to use these fatty acids. It’s the net effect that matters, not just removing carbs.

On a side note, have you heard the phrase ‘eat fat to burn fat’? It’s nonsense. Your body burns what it eats, whether it’s carbs or fats. So increasing dietary fat increasing fatty acids in the blood. This means more of them are used as fuel but it also means more are going to be stored!

So when someone says ‘eat fat to burn fat’ it should really read ‘eat less to burn fat’!

3. Insulin is not continually released

Insulin only has a half-life (degraded after) of about 10 minutes once released (5), so even if it does block lipolysis, this is only for a small portion of the day. After eating, you enter something called the postprandial and absorptive state where your body goes back to using these fatty acids.

James Krieger depicts this in the chart below.

Once again, it comes back down to energy balance as the master regulator of whether or not you lose fat.

Hopefully by now I’ve managed to convince you that it’s not the hormone or food group itself that is the enemy, but consistent overeating that leads to weight gain. Even if you ate a high sugar diet you can still lose weight (I don’t recommend this though!). (Man loses weight on only twinkles only diet

'But my friend lost 6lbs in one week'

I’m sure you’ve heard this one before. And it does happen, but unfortunately it’s not all fat. This is down to changes in water balance rather than sudden fat gain or loss. Carbohydrates are stored in our muscles as glycogen, and every part glycogen holds 3 parts water. When we eat less carbs than normal (like when we start dieting), we hold less water and deplete our glycogen stores, giving us this false illusion that we've lost fat.

So if you start your low carb diet, you will expect a sudden drop in weight, but also expect this to come right back when you start eating them again.

This is why it’s important to not only use the scales as a metric for how well you’re doing.

But some studies how low carb diets helps with weight loss??

Yep, research has shown how a low carb diet can be favourable for retaining lean body mass and a reduction in fat mass (7). However, with many of these comparison (high carb vs low carb) studies, the reduction in carbs meant a higher % of protein and we know how protein helps with weight loss (8).

In fact, in an isocaloric (kcals kept the same in both groups) diet where protein is kept constant, there was a greater fat loss in the low fat diet group (8).

How's that?!

Converting glycogen to fat (De Novo lipogenesis) is an energy demanding process (you lose 25% of the kcals), meaning it requires more kcals to convert carbs to body fat compared to storing dietary fat as body fat (9).

It’s fairy well accepted now that kcal control dictates and is the main driver for weight loss, where carbs have little effect. Once kcals and protein are equated, the composition of your fat and carbs is not going to make a huge difference on body composition.

So whether you go on a low carb or low fat diet, providing protein is kept high and you’re in an energy deficit you will lose weight.


There’s always one of these isn’t there!

The calories in vs calories out is obviously a very simplified way of looking at weight loss as there are many implications and caveats that do effect the success of a diet, where hormones do still play a huge role. This is why I always take a very context sensitive approach to diet, I sit on the fence or I know that you have to adapt eating it to the individual, goal and situation.

And it’s the same with using a low carb diet. In some cases, low carbohydrate diets can be beneficial.

In fact, a low carb or keto diet can be favourable for ‘unhealthy’ populations with some kind of metabolic dysfunction (poor glucose control, pre diabetic, hypertension etc) (11, 12). This is not to say low carb will cure all of these ailments but it could be used for therapeutic benefits.

There is also some very real practical benefits of cutting down on carbs

  • By reducing your carbohydrates you end up increasing your protein, which in turn helps with satiety, ‘no hunger, no cravings’ and the increased production of CCK, a hormone to say that you’re full.

  • The increase in protein also increases muscle protein synthesis which helps body composition

  • A drop in carbohydrates automatically reduces a lot of junk food (crisps, sweets, biscuits)

  • Cutting carbs also often results in a drop in refined sugar and processed foods - Something we know too much of can lead to all sorts of problems

  • Reducing carbs automatically cuts calories - you're eating less food!

So there are without doubt benefits of cutting back on carbs.

I think what frustrates me most about the 'low carb vs low fat' debate it that there is one in the first place.

Whichever camp or side you sit on completely disregards the idea of context, the individual, goals, training, past diet, health and preferences. This is why when it comes to choosing a diet approach to suit your situation, you have to be pragmatic and flexible in that you can adapt your eating as you move forward.

This is one of the main problems of following someone else's diet because it worked for them, just because they had some success with does not mean it will necessarily work for you.

Are you an athlete, what are your energy demands, have you any ailments, what do you like eating, what's your training setup? Unfortunately, I can’t answer all of those questions in one post!

However, when it comes to building your diet it often comes down to following a number of simple key principles I always go on about, operating a little trial and error but most importantly be consistent as after all....

Are you need in of some more help with your diet? Then get in touch ( to see how we can help.


  1. J Int Soc Sports Nutr. 2016 Jan 16;13:3. doi: 10.1186/s12970-016-0114-2. eCollection 2016. The effects of a high protein diet on indices of health and body composition--a crossover trial in resistance-trained men. Antonio J, Ellerbroek A, Silver T, Vargas L, Peacock CJ Int Soc Sports Nutr. 2016 Jan 16;13:3. doi: 10.1186/s12970-016-0114-2. eCollection 2016.

  2. Effects of dietary protein intake on body composition changes after weight loss in older adults: a systematic review and meta-analysis. Jung Eun Kim, Lauren E. O’Connor, Laura P. Sands, Mary B. Slebodnik, Wayne W.Campbell. Nutrition Reviews Mar 2016, 74 (3) 210-224; DOI: 10.1093/nutrit/nuv065

  3. Frid, Anders et al. "Effect Of Whey On Blood Glucose And Insulin Responses To Composite Breakfast And Lunch Meals In Type 2 Diabetic Subjects". The American Journal of Clinical Nutrition 82.1 (2005): 69-75. Web. 14 Oct. 2016.

  4. Gordon I. Smith, Jun Yoshino, Shannon C. Kelly, Dominic N. Reeds, Adewole Okunade, Bruce W. Patterson, Samuel Klein, Bettina Mittendorfer. High-Protein Intake during Weight Loss Therapy Eliminates the Weight-Loss-Induced Improvement in Insulin Action in Obese Postmenopausal Women. Cell Reports, 2016; 17 (3): 849 DOI: 1016/j.celrep.2016.09.047

  5. Palmer BF, Henrich WL. "Carbohydrate and insulin metabolism in chronic kidney disease". UpToDate, Inc.

  6. James Krieger. 2012. Insulin…an Undeserved Bad Reputation. [ONLINE] Available at: [Accessed 13 October 2016].

  7. Rauch JT, Silva JE, Lowery RP, et al. The effects of ketogenic dieting on skeletal muscle and fat mass. Journal of the International Society of Sports Nutrition. 2014;11(Suppl 1):P40. doi:10.1186/1550-2783-11-S1-P40.

  8. Wycherley, T, Moran, L, Clifton, p, Noakes, M, and Brinkworth, G. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Am J Clin Nutr December 2012. vol. 96 no. 6 1281-1298

  9. Hall, K. (2009). Predicting metabolic adaptation, body weight change, and energy intake in humans. AJP: Endocrinology and Metabolism, 298(3), pp.E449-E466

  10. Acheson KJ, Schutz Y, Bessard T, Anantharaman K, Flatt JP, Jéquier E. Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man.Am J Clin Nutr 1988 48: 2 240-7

  11. Volek JS, e. (2016). Comparison of a very low-carbohydrate and low-fat diet on fasting lipids, LDL subclasses, insulin resistance, and postprandial lipemic responses in... - PubMed - NCBI. [online] Available at: [Accessed 14 Oct. 2016].

  12. Samaha F, Foster GD, Makris AP, Low-carbohydrate diets, obesity, and metabolic risk factors for cardiovascular disease. Curr Atheroscler Rep.2007 Dec;9(6):441-7.

  13. Do you want to know more about this subject?

  14. People worth checking out: James Krieger, Alan Aragon, Danny Lennon, Martin Macdonald, Kevin Hall, Stu Phillips, Evelyn Soucur

  15. Worth watching - The Alan Aragon vs Gary Taubes debate


Featured Posts
Book Your Metabolism Test
White Minimalist Weight Loss Instagram Post .png
Official HYROX Gym Instagram.jpg
Get The Book!
book mockup.jpg
VO2Max Testing
Follow Us
  • Facebook Basic Square
  • Twitter Basic Square
  • Instagram Social Icon
bottom of page