To carb or not to carb?

What is the keto diet?

In a world of weight-loss diets, we’ve seen the low carbohydrate, high protein eating plans wax and wane in popularity over the years. The Aktins Diet and Keto Diet have particularly proffered the idea that carbs are inherently fattening.

But are carbs really the bad guys? Let's investigate.


Carbohydrates are essentially sugar molecules bonded together to varying degrees.

Structurally speaking, there are two types of carbohydrates. Simple carbohydrates and complex carbohydrates:

Simple Carbohydrates

Simple carbohydrates are smaller, more easily digested molecules known as mono and disaccharides. These simple sugars are also called free sugars or added sugar. Think biscuits, chocolate, flavoured yoghurts, breakfast cereals and fizzy drinks. Sugars in honey, syrups (such as maple, agave and golden) and unsweetened fruit juices, vegetable juices and smoothies occur naturally, but still count as free sugars.

Sugar found naturally in milk, whole fruit and vegetables do not count.

Complex Carbohydrates

Complex carbohydrates are called polysaccharides, since they have more than two sugar groups linked together and therefore need more digestion. Complex carbohydrates include starchy carbs and fibrous carbs. The sugar molecules in starch are bound together to a lesser degree than in fibre, hence the body is able to completely digest starch whilst it is not able to fully digest fibre. If you eat too many starch-rich foods, your body can also convert the glucose in the starch to fat.

Starch is found in roots vegetables (potatoes, beetroot, parsnips) as well as grains and products made from grains. Good sources of fibre include vegetables and fruit, wholegrains and lentils and beans.


All cells must burn fuel to function. One of the main roles of carbohydrates in the body is as a source of energy. However, not all carbs are created equal and herein lies the challenge.

The first thing to make clear is that we ALL need to keep our intake of simple carbs/free sugars to a minimum. Recent research provides compelling evidence that high GI carbohydrates are associated with an increased risk of obesity. Current guidance is to reduce sugar intake to less than 5% total energy intake, however the less the better for the majority.

For the majority

In terms of complex carbohydrates, carb reduction will cost us in the long-term as we require some complex carbs to function at our best. In fact, research shows having a very low carbohydrate diet for too long can negatively affect our healthy gut bacteria. And iIncreasing evidence demonstrates the importance of maintaining a healthy gut flora (they love complex carbs) for regulating hormones and reducing risk of diseases.

Those who could benefit from a low carb diet

Very sedentary people as well as those who have insulin resistance (a condition in which the cells of the body become insensitive to the hormone insulin) may benefit from a lower overall carb diet for a while, as part of an overall transition towards more activity and a healthier metabolism.

A small proportion of the population will be able to function with an even lower carb diet. For example, ketogenic diets (very low carbohydrate diets) are actually prescribed for people with epilepsy, as they seem to reduce their symptoms and cut down on seizure frequency. There is also preliminary evidence that ketogenic diets benefit other neurological disorders, such as Parkinson’s disease and Alzheimer’s disease.

How about athletes?

A small proportion of athletes may benefit from a very high or low carbohydrate diet. Glucose is the muscles preferred fuel, so it is therefore not surprising that the vast majority of endurance athletes do better on high carb diets versus low carb diets.

However there are exceptions. There are a few athletes who are able to perform on a low carb regime, as they are better fat adapted. Although it is worth noting that after a week of adapting to a low-carb diet, a test on cyclists found that while they could more or less perform normally, their sprint capacity did take a big hit.

In summary, while studies will show that on average athletes tend to perform better with higher carb intakes, this is not a universal rule. There is always individual variability.

As each body is different, it is recommended that you seek bespoke advice about your carbohydrate intake from a registered Dietitian or nutritionist.

Scared of carbs? Here's why you shouldn't be >

Does the keto diet help you lose weight?


The ketogenic diet is a high fat, moderate protein, low carbohydrate diet that aims to force the body into using fat as a fuel source instead of carbs This is a state known as Ketosis.

The keto diet relies on ketone bodies, a type of fuel that the liver produces from stored fat.

How does Ketosis works work?

Ketosis is reached in a few days after carb deprivation. In practice, although the exact ratio depends on your particular needs, the keto diet advocates a high fat intake. In a daily 2000kcal diet for example you would be looking to eat about 165 grams of fat, 40g of carbs and 75g of protein.

What isn't allowed:

  • Zero grains or bread allowed
  • No fruit allowed, other than berries

What is allowed

  • Vegetables like kale, swiss chard, spinach, cauliflower, broccoli, Brussels sprouts, asparagus, bell peppers, onions, mushrooms, cucumber and celery.
  • Moderate portions of protein rich foods, like beef, chicken, fish and pork
  • Lots of nuts, avocado, butter, lard and full fat dairy products allowed

What does the research say?

The keto diet is said to be an effective way to achieve weight loss. The issue is that the majority of the studies done have only produced short-term results, plus the results have been mixed.

The long-term efficacy of such a diet needs to be studied, however preliminary data suggests that the Keto diet has a negative impact on the gut flora.


The keto diet is definitely not for everyone. If you have liver or kidney problems then this diet is not for you. If you have a slow gut (i.e. constipation prone) and you currently have a higher carbohydrate intake, then you will also struggle with the diet.

However, if your current intake of carbs is already pretty low and you use the Keto as a short-term kick-start to fat loss, then it can be effective. Remember to focus on the healthier monounsaturated fats, lean protein and eat lots of greens.

References – Available on request.

Next up:

What is intermittent fasting and does it work? >

Sugar-free living: Is it feasible? >