One of the most hyped diets of the nineties and early noughties, the low carb diets reputation well and truly precedes it. While it all started with Dr Robert C Atkins of the eponymous Atkins diet in the sixties, it is regularly re-packaged under a new name with a slightly different spin. Recently, we've had the paleo and ketogenic diets.
Various low car diets are based on the premise that the body will burn fat when carbohydrate levels are kept relatively low, by cutting bread, pasta and sugar, and upping foods naturally high in fat and protein, such as meat, fish, cheese, nuts and seeds. It's vital to note that, as with most things, there are different ways of doing low carb. Some people might focus on, say, pork, beef and eggs, others might go hard on nut butter, avocados and sardines.
These can have different outcomes. A meta-analysis published in health journal The Lancet in 2018 found that: 'Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality,' whereas 'those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality.'
There isnt a precise ratio, but generally below 130g carbohydrate per day, or 26% of your intake, is considered low. The keto diet is more extreme, suggesting between 20-50g per day, or under 10%. It's important to remember that the volume of carbohydrate you need to stay healthy will depend on how active you are if you train hard multiple times a week, you need more than someone who doesn't much move their body.
Something to be aware of is that carbohydrates are not a monolith. According to the he British Dietetic Association (BDA): 'Typically, carbohydrates can be divided into the following categories:
While, ultimately, all carbs break down into glucose (sugar) in your body, simple/ free sugars will do so more quickly potentially spiking your blood sugar and causing you to feel tired and hungry, quickly. Complex or starchy carbs will break down more slowly.
The organisation also notes that there is a difference between highly processed starchy carbs, such as white bread, versus less refined carbs, like wholegrain spaghetti. The latter are more nutritionally dense.
The thinking, says dietitian Dr Carrie Ruxton, is that: all carbs break down in the body to form sugars which boost blood glucose levels and cause our bodies to produce insulin. Insulin is a storage hormone, so excess fat and carbs end up in our fat cells and liver for a rainy day. But, because people are typically sedentary, that rainy day never comes, so we end up overweight, or even diabetic.
The official stance from the BDA is that low carb weight loss is initially generally the result of fluid loss, rather than fat.
'Carbohydrate is stored in our muscles alongside water as glycogen. Drastic reduction in carbohydrate intake will lead to glycogen depletion and fluid loss. This is not the same as fat loss and not related to health or well-being. Drastic reduction in carbohydrate intakes can affect our gut health and lead to constipation. At the moment, there are no clear definitions on what "low carbohydrate" diets are. Some people claim this is an effective method of weight loss, however for some people they are not sustainable. Most of the initial weight loss seen is often associated with water/fluid losses.
'In general, it is a good idea to be aware of portion sizes of all foods including carbohydrate, however losing weight is complicated, and restricting any one food group (including carbohydrate) is generally not recommended for many reasons including dietary imbalance, contributing to complex relationships with food and compliance.'
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The main benefit of a low carb diet is the potential for weight loss. Research has found to be more effective in the short-term but, over longer amounts of time, its similar from other diets where intake of calories is restricted.
Low calorie diets probably work simply by restricting opportunities for consumption, says Dr Buxton.
Low carbohydrate diets have been found to potentially benefit type 2 diabetes and those at risk of developing it.
However dietitian Paul McArdle says: Theres no universal recommendation as yet for how much carbohydrate is best for type 2 diabetes which is why we should take a whole diet approach and not just focus on single nutrients.
(Don't start a low carb diet without speaking to a doctor as it can affect diabetes medication.)
A fairly new claim, its been suggested that low carb diets can improve fertility by some experts. As well as tackling obesity, which is linked to issues getting pregnant, research has shown that they can improve levels of reproductive hormones. Note: this is not advice across the board. The NHS states that in pregnancy, starchy carbs should 'make up just over a third of the food you eat. Instead of refined starchy (white) food, choose wholegrain or higher-fibre options such as wholewheat pasta, brown rice or simply leaving the skins on potatoes.'
As foods that are high in fat and protein are low in fibre, it can have a knock-on effect on gut health. 'Fibre keeps your gut healthy and you may get constipated if your diet is too low in it', says Dr Ruxton.
Though low carb diets can be effective in the short term for losing weight, which can benefit CVD, long-term theyre linked to increased levels.
Diets low in carbs have been shown, in one small study, to affect reaction time and visuospatial memory, despite reports of improved vigilance. 'Our brains actually run most efficiently on glucose, which is what all carbohydrates break down to in the body', says Panagos.
From carb-rich fruits like apples to various types of grain, avoiding carbs means forgoing a lot of nutritious foods.
The first meal of the day seems to be the one people need most inspiration for, when starting a new food routine. A low carb breakfast could be greek yoghurt with raspberries and pumpkin seeds, a mushroom omelette with grilled tomato or simply bacon and eggs.
It depends. They're always inadvisable if you're on medication, especially for diabetes, however research has seen some benefits when following in the short-term.
'Low carb diets are safe, but may not be balanced if you go too low', says Dr Ruxton. 'Carbohydrates are important sources of dietary fibre, so you would need to eat more vegetables, pulses, beans, nuts and seeds to make up for the loss.'
'Foods that contain carbohydrates are an important part of our diets and can be included in as part of a healthy balanced diet,' the BDA's take. 'It's helpful to choose wholegrain starchy carbohydrates as they contain additional important nutrients for the body. As with any food, it is important to choose the correct portion to suit your needs and less active individuals require less carbohydrate. Its useful to be aware that free sugars often provide lots of energy with very little nutritional value so these should be consumed in moderation.'
The keto diet is a low carb diet, but its just the name for an extreme restriction which causes ketosis, the process that happens when the body doesnt have enough carbohydrate to burn for energy so it burns protein and fat, and makes ketones. It happens in a less carb limited diet, but just in between meals rather than all the time.
Speak to your GP before starting a new diet and dont embark on a low carb plan if youre breastfeeding or taking medication for high blood pressure or diabetes.
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Is Following a Low Carb Diet a Safe Way to Lose Weight?
