The Ultimate Guide to Simplifying Diet: Part 4 – Carb Controversy


The pendulum swings in nutrition tend to be extreme.

Last week, we looked at dietary fat: vilified from the 1960’s to circa.200-something, and now experiencing a comeback so dramatic that some people put duck fat in coffee.

Carbs exist in a similar continuum. A string of research through the 90’s and 00’s seemed to suggest an unequivocal superiority of low-carb diets for weight loss. Was this the nutrition Holy Grail we’d all been looking for? Were carbs really making us fat, independent of overall calorie intake?

Carbs Will Not Magically Make You Fat

It is the realm of pure fantasy to suggest that any macronutrient – protein, carb or fat – can make you gain weight on it’s own and without you eating a calorie surplus. 

Carbs will not magically make you fat: chronic intake of excess energy will.

Weight loss diets have consistently been successful if, and only if, they create a calorie deficit, regardless of whether the diet is lower or higher in carbs.  

And the studies that seemed to show greater weight loss on a low-carb vs. low-fat diet? They cheated, kinda…by not matching the protein intake between the diets, the real comparison was actually a high-protein/low-carb vs. low-protein/low-fat diet – and higher protein diets do lead to greater weight loss.

So, if you lose weight on a low carb diet, it is cause and effect – by cutting out an entire macronutrient and food group, you’ve already dropped calories, and also started eating more protein. 

What Carbs Will Do For Your Health

This does depend – like the concept of “good” vs. “bad” fats, we can take a similar view of carbohydrates.

The general public health advice for the past 60 years to reduce fat consumption recommended replacing fat in the diet with carbohydrate. Unfortunately, the advice didn’t stress too much on type of carbohydrate, and in the free-market economy with open advertising, that gap was filled by food industry, calling on everyone to shovel in Frosties for breakfast and drink Coke.

Extrinsic sugars in the diet are a big problem, because increasing energy in the diet from sugar leads to overconsumption of energy overallThis has been one of the major drivers of obesity and type-2 diabetes.

Beyond obesitythere is strong evidence for the type of carbohydrate influencing cardiovascular diseaserefined carbohydrates increase risk, while wholegrain, unrefined, high-fibre carbs lower risk.

This brings me to one of the big variables in nutrition and health: dietary fibre. Dietary fibre may be directly protective against cardiovascular diseaseIn fact, and extra 10g of fibre per day can reduce your risk of CVD by 32%.

With regard to obesity, fibre increases satiety hormones and leads to greater adherence, which in turn leads to reduced calories over time and weight loss. The same positive associations are seen between increasing dietary fibre and better blood glucose regulation in diabetics.

Short-chain fatty acids synthesised from fibre by bacteria in the colon not only reduce inflammation and boost the immune systemthey also suppress tumour genes in colon cancer.

(For more on fibre, read this and this).

And what about for otherwise healthy individuals? For those power sport enthusiasts amongst you – swimmers, rowers, cyclists, Crossfitters – carbs are the primary fuel source in the body at exercise intensities above 75% of your VO2 max, and low muscle glycogen levels result in impaired performance of high-intensity training. The same effect is seen in strength sports – sprinting, powerlifting and bodybuilding.

And for the marathon runners amongst you, there is an interesting twist. While low glycogen stores negatively effect endurance performance, training in a glycogen-depleted, low-carb state can increase the aerobic adaptations to exerciseThis had led to the concept of “train low, compete high” – performing intermittent training sessions in glycogen-depletion to increase aerobic adaptations, then doing the race in a high-carb, glycogen-loaded state.

Turning Carb Timing On It’s Head

“Conventional wisdom” tells us that we should all eat our carbs in the morning, and avoid them in the evening. Or after 3pm. Or completely.

Nonsense. What if it was the opposite? I imagine you’d be happy. I was.

In fact, early morning carbs may be doing more harm than good, by stimulating post-breakfast hunger and leading to more overall calories consumed.

Substituting your morning carbs for protein may be the weight loss hack you’ve been looking for – an average of 30-40g protein at breakfast leads to greater appetite suppression, and less calories consumed at lunch.

But this doesn’t mean we need to avoid carbs at all times. On the contrary. Eat them in the evening

What’s that, you scream, heresy?! Not so much – eating a majority of carbs in the evening leads to greater weight loss compared with spreading carbs throughout the day. 

Low-carb evenings will also affect your sleep, reducing time spent in restorative REM sleep, and increasing sleep onset latency. On the other hand, evening carbs can promote sleep by increasing brain concentrations of the amino acid tryptophan, which in turn increases melatonin levels.

This simple manipulation of your diet can help keep you full, lose weight and sleep better; emphasise protein and fat in the early part of the day and shift your main carb meal to the evening.

Tailor Your Carb Intake to Your Activity Level/Type

As we discussed above, if you are a strength/power or endurance athlete, you will need more carbs than a sedentary office worker to maintain performance and enhance recovery.

In people who are overweight/obese or pre-diabetic/diabetic, one of the major metabolic issues is insulin resistance i.e. their body cannot properly regulate blood glucose levels, leading to multiple physiological impairments including an inability to process carbs, utilise stored fat, and increases in circulating triglycerides.

While reducing calorie intake and losing weight will improve these issues, independent of diet composition, a l0w-carb diet can be a very effective short-term strategy to improve insulin function and reduce triglyceride levels.

For sedentary office worker types, I tend to lean on a higher protein/lower carb approach, because of the satiating, appetite-reducing effects of higher protein diets, which can help a sedentary person from eating more than their already low energy requirements.

But no one should be sedentary. I am going to assume you have some form of exercise in your life. In that case, incorporate some nutrient dense, high fibre starchy carbs into your diet – lentils, beans, chickpeas, quinoa, rice, potatoes (sweet, white, red), couscous – to balance your diet, fuel performance and recovery, and diversify your micronutrient intake.

And for portion sizes? Again, I refer you herepalm for protein, fist for carbs, thumb for fat. Simple.

Rapid Fire Roundup

Carbs won’t make you fat. Too many calories will. Extrinsic sugars and refined carbs can lead to too many calories consumed, keep your sweet tooth to “10% foods.”

You have nothing to fear from unrefined, unprocessed and high fibre carbs.

If you’re overweight, a low-carb diet can help in the short-term, but adherence is all the matters in the long-term. If low-carb doesn’t equal adherence for you, you are only cheating yourself.

Carbs are pretty vital to sports performance.

Everything you were told about carb timing was a result of marketing by breakfast cereal companies. Turn that on it’s head. Keep carbs light during the morning, bump up your breakfast protein, and keep you main carb meal for the evening.

*Drops the mike*