Cutting out carbs has always been a fashionable way to lose a few pounds. From The Atkins Diet in the 1980s to the Keto Diet in 2018, carbs often get a bad rep when it comes to trying to manage our weight.
Over recent years there has been some high-profile doubt cast over the Government’s recommendations on carbohydrates, with some parties staunchly advocating that our current Eat Well Guide recommendations to base our diets on starchy carbohydrates are outdated.
‘The research evidence supporting carbohydrates as being a causal factor in the obesity epidemic is far from conclusive’
But despite the growing public interest in reducing carbohydrates and high-profile debate, the evidence supporting carbohydrates as being a causal factor in the obesity epidemic is far from conclusive.
While few would dispute the negative effects of free sugars (sugary drinks and foods where sugar has been added where it doesn’t occur naturally) on our risk of obesity and therefore poor health, research does not support the reduction of starchy carbohydrates like bread, pasta, rice and potatoes for long-term health.
Low carb diets can be effective for short term weight loss
Despite significant exploration, the only thing we can truly conclude from the latest research is that low carb diets can be an effective strategy for some people to control their weight in the short term.
In September 2018, a study was published in The Lancet which reviewed the diets of over 15,000 people in the US and looked at all causes of death.
This research group found a ‘U shape’ relationship exists with our carbohydrate intake and risk of death. That means those consuming really high levels of carbohydrate (more than 70 per cent of energy) are at greater risk of poor health and ultimately death but those consuming very little carbohydrate (less than 40 per cent of energy) face even worse health outcomes.
Something that is restricted on a low carbohydrate diet is fibre, which has recently been recognised for its vital role in the prevention of disease.
Since the demonisation of carbs, many people have swapped high-fibre breakfast cereal for eggs and bacon and cut out wholegrains. Adding more vegetables and lentils is the solution to this but we know that constipation (caused by a lack of dietary fibre) is a major side effect of low carb diets and some of the types of fibre needed to optimise our colonic bacteria can only come from wholegrains like wheat.
The sweet spot: 50-55 per cent of energy from carbs
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So even though low carb diets may help some people to lose weight, they are still associated with a greater risk of death from preventable disease.
The sweet spot for carb consumption seems to be when we hit around 50 to 55 per cent of energy from carbohydrates. This would equate to around 1,000 calories worth of carbs for the average, active adult which is a portion with each meal.
What is really important to note is that what we replace the carbs with on a low carb diet appears to have a massive impact on our health outcomes.
‘Researchers found if we replace them with plant-based proteins such as nuts and vegetables, our risk of death decreases’
For example, the researchers noted when we replace carbs with animal-derived protein and fat sources like meat, our risk of death increases, but if we replace them with plant-based proteins such as nuts and vegetables, our risk of death decreases.
This puts the Atkins Diet and those having extra cheese, bacon and mayo on their burger instead of a bun on dodgy ground health wise.
Mediterranean diet associated with much lower risk of disease
When we think about health at a population level and the dietary habits that are prevalent in populations with the lowest risk of disease, the latest studies still support the Mediterranean diet as being a dietary pattern associated with a much lower risk of disease when compared to Western dietary patterns. The Mediterranean diet is based on starchy carbohydrates as per the UK Eat Well guidelines.
When we look beyond Europe, recent studies have noted the Japanese diet is also associated with a reduced overall risk of death from non-communicable disease with particular links to cancer prevention. While the characteristics of the Japanese diet have yet to be formally defined, it is recognised that rice is a key food staple in this population.
‘The dietary pattern associated with reduced risk of death from preventable disease is one that is based on starchy carbohydrates’
This means in studies of US populations, European populations and Japanese populations, the dietary pattern associated with reduced risk of death from preventable disease is one that is based on starchy carbohydrates.
All dietary data is imperfect because of the impact of environmental factors, physical activity, smoking status and many other things on health outcomes. But there is certainly convincing evidence that at a population level, the best advice for the prevention of disease is still to base our diets on starchy carbohydrates.
That said, obesity levels in the UK remain relatively static at 26 per cent of the population, and we know conclusively that being overweight or obese leads to worse health outcomes for individuals.
We shouldn’t demonise food groups
For that reason, strategies to support weight reduction at an individual level are important but there is not a ‘one-size-fits-all’ solution to weight loss and low carb diets are far from being the only solution.
People should consider questions around why they are overeating rather than cutting out food groups or downloading the latest fad diet. Everyone knows that eating more vegetables, protein and wholegrain would lead to better health. The solution to maintaining a healthy weight lies in understanding why we are not able to achieve this, not in demonising carbs or any other food group.
The best evidence we have to date supports the inclusion of carbohydrates as part of a balanced diet for the prevention of disease and those with the lowest risk of disease are consuming carbs with most meals.
Sophie Medlin is the lead dietitian at CityDietitians (CityDietitians.co.uk) and a lecturer in Nutrition and Dietetics at King’s College London.
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