A low carb diet or a low fat diet?

LARD!Uhn, are you taking this Atkins thing too far?

There’s endless debate about what type of diet is best. A low carb diet? A Low fat diet? There’s a huge variety of options, and in the book we looked as issues like the ‘Nutrition Hierarchy’ and the types of rules that we going to help you piece together a diet right for your goals. We discussed how, though people will always try and focus on different issues, it is still the calories that are the foundation, how the balance of macronutrients may have a huge impact on what you see in the mirror, but at the end of the day you still have to think about food choices.

So, to set the scene, for the last 40+ years low fat diets have been pushed for health and weight loss, they have their roots in the work done by Ancel Keys and the subsequent government health work (massive over-simplification there), governmental health organisations have been basing their advice on them for the last 30 odd years, and  the result have not been good.

As with many things we tend to like to swing between extremes and low carb or virtually carb free diets are a popular way to reduce fat. There’s a bunch of these low carb diets about, the most famous of course is Atkins, popularised by a doctor of the same name, they have in their roots in therapeutic diets used in clinical situations. But that doesn’t mean they’re right for general use.

High fat versus low fat compared.

When you look at the literature you find that there’s not a huge amount difference in the efficacy of higher fat versus lower fat diets for the general population. The upshot is that the best way to lose weight is reduce calories. For the very overweight and those with diabetes then the balance of evidence suggests that lower carb is the way to go, initially at least. Keep in mind though that is the ‘lower carb than the standard diet’ not “low carb”.

Looking more specifically at the literature on intermittent fasting you find firstly there’s very little, comparing low carb and low fat, but that both high fat and low fat conditions do lose weight (body fat mass) using IF, however  if maximising the benefits for the cardiovascular system are your goal then a a more moderated/lower fat diet holds some modest benefits.

The thing is that IF appears to be a real winner because you see a lot more fat lost vs muscle. Muscle is of course useful and an endocrine tissue helping to regulate whole body metabolism.

The problem with both fat and carbs

There’s another factor and that is energy balance, both high fat and high carb diets have a similar issue – they’re an easy way to over eat energy. Fat is not, calorie-for-calorie, very filling. There’s been research where they sneak fat into meals/diet and there’s not really a reduction in the amount eaten. This is bad news as you end up taking more calories on board. Similarly carbohydrate is highly palatable and, in the right forms very easy to overeat.

High/Low carb have different implications when thinking in terms of the hormonal milieu and the setting of this – the persons body. Certainly we now understand that higher fat diets are as harmful as we once thought they were, and there seems to be a picture emerging that lower carb diets can be tolerable and beneficial long term. On the flip side higher carb and low fat diets have a long history of success in all levels of bodybuilding allowing men and women to get to very low levels of body fat, here levels of insulin sensitivity, activity and muscle mass may be an issue.

So there’s not much to go on there, but wait, you may have spotted the obvious though: we forgot something … 


The Missing Factor.

What sits next to that ‘high carb’ or ‘high fat’ meal? Protein, and protein may well be the real deal breaker here.

High protein diets are in the real world becoming much more popular for fat loss and also general health. In science it is true to say the evidence mounts. Protein is considered to be much more filling that either carbs or fats. Thermogenesis, the ‘leaking’ of energy out of your body – energy that once gone can’t be stored – is also higher on high protein diets. Other more contentious arguments include looking at insulin, which (because you’ve read the book!) you know has an important role in fat deposition and keeping it in storage and so on.

The research also shows that ability of higher protein diets to spare muscle when losing ‘weight’. Indiscriminate ‘weight loss’ is not necessarily good. what people need is fat loss, and to hold on to muscle whilst they do it. The literature shows the power of protein to help you here.

As ever there’s not 100% agreement in the science and it’s hard to compare many of the studies as there’s not real definition of ‘high protein’, that said the body of evidence is pretty good.

My advice

High protein teamed with good carb a fat choices is the way to go here. The higher protein Mediterranean style diet is a very good way to go. It’s satiating – it will fill you up, it’s great for supporting weight-loss and it is a big winner on factors like cardiovascular health. Of course teamed with fasting it can be even better.

I’ll generally push non-athlete clients towards a lower carbohydrate end of the scale, with plenty of ‘healthy’ protein and ‘healthy’ fats and oils. How many grams of carbs? That depends, but in practice forget counting grams of carbs the meals and diet structure is is the focus, with  carbohydrate kept to one or two feedings a day. Research supports this as  an easy way to weight loss and weight management. Athletes are different, I’ll tend to give them as much carbohydrate as they need to perform and alter fat intake accordingly. Note though that that amount may change through the week (a la carb cycling, train low, compete high etc), and that also protein in both cases will stay pretty constant.

but in practice forget counting grams of carbs the meals and diet structure is is the focus, with  carbohydrate kept to one or two feedings a day

So what to do

  • Step ONE: Set you protein intake

This is the most important step. For most people looking at about 1.4-1.7 g rams of protein per kilo bodyweight. For athletes especially strength and power athletes or those looking for a bit more muscle (and less fat) you’ll need a minimum of 2g/kg bodyweight.

Keep those sources varied, focus on foods and the protein MUST be complete and concentrated sources. Have a look at the FOOD TABLES here for your choices.

  • Step TWO: Look at what type of meals you prefer to eat

For this to work, it is going to have to work long term. So, what type of eater are you? Think about the healthy lower fat versus healthy lower carb foods, which do you prefer to cook and to eat?

If you have specific needs like being very overweight or having blood sugar regulation issues then this will alter you needs, for example in the very overweight lower carb options do better.

Remember also that you can have lower fat meals and lower carb meals in the same day. A common techique is to have a low fat higher carb meal – for example pasta and lean meat sauce – after training, then at some other time a lower carb meal, like salad with chicken and avocado.

  • Step THREE: Eat 

For BOTH lower carb or lower fat choices it is what you eat that counts, this means for the low fat people forget diet foods, most of these are total rubbish, keep the sugar intake down focusing instead on minimally processed high nutrient density carbs. For both groups focus on high quality fats and fatty foods.If going higher carb then you’ll need to keep fats low and really make sure they’re high quality (oily fish, olive oil etc).

This isn’t an excuse for sugar binges and ‘Low fat’ processed foods and similarly if going low carb, it isn’t a cheese and bacon fest. Both groups need to also make sure the fat is high quality and also keep eating the colourful fibrous veg.


Low fat and low carb each have their pros and cons, their supporters and detractors, either way the focus should be on quality od the foods and nutrients you’re eating (especially with the fats), and you should dial in your protein. Really what you prefer to eat from a behaviour and preference point of view is such a strong driver of ‘success’ that, as a species, us omnivores can get away with big variations in  carbs versus fats – just get your proteins.


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Barkeling, B., Rössner, S., & Björvell, H. (1990). Effects of a high-protein meal (meat) and a high-carbohydrate meal (vegetarian) on satiety measured by automated computerized monitoring of subsequent food intake, motivation to eat and food preferences. International journal of obesity14(9), 743-751.

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Westerterp-Plantenga, M. S., Rolland, V., Wilson, S. A. J., & Westerterp, K. R. (1999). Satiety related to 24 h diet-induced thermogenesis during high protein/carbohydrate vs high fat diets measured in a respiration chamber.European journal of clinical nutrition53(6), 495-502.

Cotton, J. R., Burley, V. J., Weststrate, J. A., & Bhmdell, J. E. (1994). Dietary fat and appetite: similarities and differences in the satiating effect of meals supplemented with either fat or carbohydrate*†. Journal of Human Nutrition and Dietetics7(1), 11-24.

Elhayany, A., Lustman, A., Abel, R., Attal‐Singer, J., & Vinker, S. (2010). A low carbohydrate Mediterranean diet improves cardiovascular risk factors and diabetes control among overweight patients with type 2 diabetes mellitus: a 1‐year prospective randomized intervention study. Diabetes, Obesity and Metabolism12(3), 204-209.

Klempel, M. C., Kroeger, C. M., Bhutani, S., Trepanowski, J. F., & Varady, K. A. (2012). Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutr J11(98), 4.

Klempel, M. C., Kroeger, C. M., Bhutani, S., Trepanowski, J. F., & Varady, K. A. (2012). Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutr J11(98), 4.

Klempel, M. C., Kroeger, C. M., Norkeviciute, E., Goslawski, M., Phillips, S. A., & Varady, K. A. (2013). Benefit of a low-fat over high-fat diet on vascular health during alternate day fasting. Nutrition & diabetes3(5), e71.

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