The big fat debate about carbohydrates
I recently wrote a piece about food myths, which was unfortunately given the headline “carbs don’t make you fat”, and whilst slightly misguided, not completely wrong. Interestingly, of all the myths mentioned, the focus of readers was “not all carbohydrates make you fat”. Amongst other things, the main lesson learnt was not to read people’s comments in the Daily Mail!
After reading more around the topic, it’s become clear that the debate over fat versus carbohydrates is still controversial and not something I intended to be part of. Seeing how the content of my article was spun by readers (many of whom simply commented on the headline without reading the article) only proved my thinking behind the myth as many related the information to their own personal experiences, which can’t be applied to the general population. People have different lifestyles and energy needs so it’s difficult to generalise about fats and carbohydrates.
I still stand by my view that not all carbohydrates make you fat but accept that the topic requires more explanation to comment on both sides of the debate and cannot be summed up in two paragraphs of a health article!
My clients and training
I also received many negative comments about my training and clients I choose to work with and feel I need to fight my corner! I’m happy to be completely transparent about my work.
Firstly, I’m not a vegan (not sure where that one came from!). Even if I were, then this would still not impact on my views about carbohydrates. I’m a registered nutritionist with the UK Association for Nutrition and have a BSc in nutrition (not nutritional Therapy) and a MSc in public health nutrition. I currently work with food companies, mostly restaurants to improve the quality of their food and help them to meet legislation that provides transparency to customers about the food on their menus. I also work with care homes to improve the food offered to residents with dementia as well as schools and nurseries to ensure the nutritional needs of our vulnerable population groups are met.
I currently work with one of the UK’s largest supplement companies as their head of nutrition in a role that requires me to objectively ensure the right information is given to customers within the strict legislation around health claims. I don’t promote unnecessary use of supplements and stick with a message and belief of food first. Most importantly, I’m independent and simply use the scientific facts as a basis for my writing and not those of commercial companies.
I have written a recipe book with my good friend Lily called ‘The Detox Kitchen Bible’ and we exclude wheat, dairy and refined sugar from our food (which was initially based on the needs of the clients we deliver food to who include vegans and those with diagnosed food intolerances). I hold my hands up that the word ‘detox’ has bad connotations, but our ethos is to cook from fresh and focus on including lots of nourishing foods that ensure nutrient balance (including carbohydrates) rather than those excluded.
Nutrition is a science
At its core, nutrition is simple; eat healthy foods in the right portion size for your energy needs, don’t fear food or categorise as good and bad and understand there is room for all foods as part of a balanced diet. Putting this into practice is more difficult and is influenced by other factors such as behaviour change, food access, income, cooking skills and the information made available. We all know when we’re eating the wrong foods and don’t need to be patronised by health professionals like me, however, those interested in health often like to learn more about the subject.
Nutrition is also a science and research will continue to emerge that questions traditional thinking. Understanding how to read scientific papers requires training and reporting about health in the media often focuses on the initial findings of studies and those that can’t be translated to everyday life such as animal studies or those carried out on small study groups. Reporting these findings undoubtedly causes some confusion and frustration as often the messages contradict themselves between articles.
I try to avoid focusing on a single aspect of any diet and prefer to keep the bigger picture in mind as there are many challenges facing public health nutrition, but here are my views about carbohydrates and in particular their impact on weight.
Carbohydrates are one of the three macronutrients that provide energy, along with proteins and fats and an excess of any one will cause weight gain. Most foods contain a combination of these nutrients so blaming a single food or nutrient for weight gain makes little sense. There are also other factors that influence weight as mentioned above but these are not relevant to the question at hand.
Yes, carbohydrates raise insulin levels that can trigger the uptake of fat, but not before the body has taken what it needs for energy. The role of insulin is to regulate the usage and storage of both glucose and fat. This hormone controls blood glucose levels by messaging muscle, liver and fat cells to take up glucose from the blood, which is used for energy. When the body has enough to meet its energy needs, glucose is taken up by the liver and muscles to be stored as glycogen. Once the liver has stored all the glycogen it can, fat cells take up glucose and store it as triglycerides. Insulin also inhibits the breakdown of fat, glycogen stores and proteins as well as the pathway that produces ketones (more on that later).
It’s also worth noting that energy metabolism is not an all or nothing process and the body will use fat and glycogen stores simultaneously in response to its needs.
However, just because you eat carbohydrates doesn’t necessarily mean a sudden rise in fat storage! People have different energy requirements relating to their lifestyle (particularly exercise) and not everyone needs to lose weight.
You can’t lump all carbs together
Brown rice and quinoa are not the same as calorie-laden pizza and chips that also contain high amounts of fat and other nutrients such as sodium, which can negatively impact on your health. Wholegrain carbohydrates contain fibre, which is lacking in the UK diet, as well as other essential nutrients such as magnesium and B vitamins. Foods made with flour, mostly white (fortified in the UK with calcium, iron, thiamin and nicotinic acid), also provide valuable nutrients, which are especially beneficial for those on a low food budget.
A far as low fat diets versus low carbohydrate is concerned then the science behind them does differ and as explained above, an excess of glucose will be stored as fat and effect how the body utilises these nutrients for energy.
The traditional low fat diet
The traditional dietary advice for losing weight is to follow a low fat diet and is favoured by the Department of Health. The principles are that you cut down on your overall intake of fat, which helps to reduce your overall calorie intake and so lead to a steady reduction in body weight over time, an approach that many consider easier to maintain in the long-term as opposed to short-term fashionable diets.
The low fat diet also requires sticking to a reduced number of calories and endorses following other key healthy eating messages such as reducing your intake of saturated fat and sugar, eating oily fish and plenty of high-fibre foods such as wholegrains, pulses, fruits and vegetables, which will benefit long-term health. There is no recommendation in this diet to reduce your carbohydrate intake but guidance suggests that half your daily calories should come from foods rich in this nutrient and that you should opt for those that are unprocessed. High fibre carbohydrates have also been shown to help with weight loss as they have a filling effect, especially when eaten with protein and healthy fats that slow down the release of sugar.
Health bodies including the Department of Health worry that low carbohydrate diets encourage the intake of saturated fat that may impact on your risk of heart disease, however research shows that a moderately low carbohydrate diet may benefit the heart as long as proteins and fats come from healthy sources (1).
Some researchers believe that saturated fat may not be such a major factor in the development of heart disease compared to other dietary habits such as an excessively high intake of carbohydrate foods including sugar. Whilst this is a whole other issue it adds another dimension to the low fat versus low carbohydrate debate.
The low carbohydrate diet
Diets such as Atkins remove virtually all carbohydrates from the diet during their initial phases (prescribes just 40g of carbohydrate daily, which is the equivalent to about two slices of bread). In the absence of glucose from carbohydrates, the body is forced to use some protein and also fat stores for energy. Fats are converted to ketones that the body uses to supply energy to cells of organs such as the brain that usually favour glucose. In essence, your body is burning fat, which is the basis for the weight loss and loss of fat tissue, the latter of which is generally better for your health.
Low carbohydrate diets are effective, which is backed up by plenty of studies that report quicker weight losses and reductions in body fat compared to a traditional low fat diet (2, 3, 4). Researchers have even suggested that this may be a better approach for treating obesity. However, low fat diets can also help you to lose weight and studies have shown that both low fat and low carbohydrate diets can lead to significant weight losses (5). It’s also not fully clear how significant the weight losses are in the long term between the two approaches, although it’s been suggested that both are similar over time. Diets high in protein are also very satiating, which can lower overall calorie intake.
Its also worth noting that glycogen can make muscle tissues hold on to extra water, which may reflect the numbers on your scales. This is one reason why drastically cutting back on carbohydrates can initially result in a quick loss of weight as you use up glycogen stores and with that, lose water.
A recent study looked promising to finally end the debate about low carbohydrate diets versus low fat diets but as is the case with nutrition, it only provided another take on the debate and little to sway the argument either way (summed up nicely by NHS choices).
Diets are temporary
Diets are considered by most to be temporary, meaning they have an end goal. However you decide to lose weight, bear in mind, its important to think about how you’re going to keep the weight off that you have worked so hard to lose. My advice is to focus on adopting small realistic changes that can be followed through to the way you eat after you have lost the weight, whether that’s to eat less processed carbs, serve smaller portion sizes or choose low fat varieties of dairy foods.
You can’t generalise about food intake
Interestingly, my concerns from the article were only proven by readers comments, many of which favoured the low carbohydrate approach. Everyone has his or her own personal experiences, some react badly to gluten and wheat so cutting out certain carbohydrate foods is necessary and others have had more success losing weight following a low carbohydrate diet rather than a low fat approach. However, when advising public health, the message has to meet the needs of everyone in a way that is easily understood and able to be applied.
Whilst the low carbohydrate approach is convincing, these diets are not that straight forward, especially those that include different phases of carbohydrate intake and require the body to enter ketosis in order to achieve the fat burning state. It’s hard to see how this could be relayed to the general public and the last thing you want is for ketosis to be considered a healthy body state, especially for those with underlying health conditions. Saying that there may be some benefit to cutting down on your carbohydrate intake.
Yes, a diet high in sugar, pizza, pasta with creamy sauces or toast laden with butter and jam will encourage weight gain, especially when partnered with a sedentary lifestyle and excess calories but including carbohydrate foods, especially unprocessed, in the right portion size, will not.
When you talk about carbohydrate foods, many people automatically refer to cases of high calorie diets laden with large amounts of sugar and foods mentioned above, which are linked with obesity and other diet related diseases such as heart disease. For those with a healthy weight and active lifestyle, there is no reason to completely remove them from the diet.
There are many books citing the perils of carbohydrates (namely processed) and especially sugar. Whilst these are very valid arguments backed up by credible research, our body’s are more than capable of dealing with this food group in the diet, dare I say, even a little sugar. Ill health occurs in those who are over consuming large quantities of all foods including an excess of sugary processed carbohydrates; a diet that is typical in those with other unhealthy dietary habits and lifestyles.
My concerns about vilifying carbohydrates
My main concerns include:
- People self-diagnosing food intolerances and allergies resulting in unnecessarily removing food groups, potentially putting them at risk of nutrient imbalances.
- These food views getting filtered down to feeding young children and other vulnerable groups.
- Labelling foods as bad, which encourages an unhealthy relationship with food.
- The idea that all carbohydrates are the same. Eating a portion of foods rich in complex carbohydrates such as wholegrains, starchy vegetables and pulses is not necessarily the same as eating the same serving size of sugar.
The most effective diet is one you can stick with
In my opinion, if you’re trying to lose weight, which seems to be the main association with carbohydrates in the diet, then the decision of what diet to choose is really up to you and there is no right or wrong approach as sticking to either low fat or low carbohydrate will result in weight loss.
Unfortunately, the media exposure of research and debating on the topic has detracted away from the fact that the most effective diet is going to be the one that you stick with. Dr Susan Jebb at the MRC Cambridge summed the situation up perfectly with the comment, “there is too much significance placed on the nutritional composition of diets when the biggest challenge is finding strategies that help people to adhere to them”.
My point still stands, carbohydrates are a beneficial nutrient and choosing the right foods (preferably opting for unprocessed grains), in the right portion size as part of a balanced diet tailored to meet your energy needs poses no serious threat to health.
- Halton TL, Willett WC, Liu S, et al (2006). Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med. 355:1991-2002.
- Hu T1, Mills KT, Yao L, Demanelis K, Eloustaz M, Yancy WS Jr, Kelly TN, He J, Bazzano LA (2012). Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials. Am J Epidemiol. Oct 1;176 Suppl 7:S44-54.
- Foster GD, Wyatt HR, Hill JO, et al (2003). A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 2003;348:2082-90.
- Samaha FF, Iqbal N, Seshadri P, et al (2003). A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 348:2074-81.
- Una Bradley, Michelle Spence, C. Hamish Courtney, Michelle C, McKinley, Cieran N. Ennis, David R. McCance, Jane McEneny, Patrick M. Bell, Ian S. Young and Steven J. Hunter (2009). Low-Fat Versus Low-Carbohydrate Weight Reduction Diets Effects on Weight Loss, Insulin Resistance, and Cardiovascular Risk: A Randomized Control Trial. Diabetes. Dec; 58(12): 2741–2748