There has been much media hype surrounding the low carbohydrate diet. This way of eating has become recently fashionable as the Paleolithic or Paleo diet and was previously well-known as the Atkins’ diet. It proposes the key to weight loss and healthy living through drastically cutting back on carbohydrate foods such as bread, pasta and potatoes while still eating bacon, butter and cream contrary to current expert advice.
What is a low carb diet?
The low carbohydrate, or low carb diet, restricts carbohydrate consumption and replaces carbohydrate-containing foods with foods higher in fat and protein and foods low in carbohydrate. It is popular among those aiming to lose weight and is based on the idea that carbohydrates lead to weight gain. Foods commonly consumed as part of the low carb diet include fatty cuts of beef, chicken, bacon, fish, eggs, non-starchy vegetables, cream, butter, coconut oil, nuts, seeds, and non-reduced fat cheese while restricting grain foods such as breads and cereals, many types of fruit, legumes and starchy vegetables. While some recommendations support scientific evidence, many of the foundations of the low carb diet oppose current nutritional recommendations.
Where are carbohydrates found?
Common sources of carbohydrate include grain foods such as breads, breakfast cereal, rice, pasta, noodles and crackers. However, carbohydrate is found not only in grain and cereal foods, but also in fruits, vegetables such as potatoes, pumpkin, and corn, legumes such as lentils, chickpeas and baked beans, dairy foods including milk and yoghurt, table sugar and honey.1 The importance of carbohydrates can be illustrated by their presence in four of the five core food groups.
What are the benefits of carbohydrate?
Carbohydrates are an important source of energy for the body. They provide the only source of energy for many vital organs including the brain, central nervous system and kidneys.2 Not only do carbohydrate-containing foods contain many other nutrients such as protein, iron, thiamine, folate, iodine, vitamin C, beta-carotene, calcium, riboflavin and vitamin B12, many also contain fibre which is known to prevent constipation, assist with diabetes management and protect against cardiovascular disease.3,4,5 Fibre also keeps the stomach feeling fuller for longer and supports good bacteria in the gut which is essential for a healthy digestive system.
So how much carbohydrate?
The Acceptable Macronutrient Distribution Range for healthy adults and children recommends 45-60% of total energy intake comes from carbohydrates which is influenced by age, gender and level of physical activity.6 This range was set based on an increased risk of obesity with low carbohydrate, high fat intakes (<45%) and an increased risk of chronic disease, and inadequate micronutrient intake outside this range.7 Feinmann et al defined a low carbohydrate diet based on a collation of previous publications as <130g/day or <26% total energy intake which is well below the recommended range.8
Low carbohydrate and weight loss
It has been established that blaming one nutrient for the obesity epidemic or claiming another as the elixir of life is too simplistic. The idea that carbohydrate causes weight gain is also misleading as weight gain occurs when energy intake from any food source is greater than total energy expenditure, whether that be of foods low or high in carbohydrate for example. Interesting to note is the energy density of the nutrients of interest, where 18kJ/g is provided by carbohydrate and protein, with 38kJ/g provided from fat.7 When considering energy balance, it seems counterintuitive to replace a more energy dense nutrient with one that is less energy dense to support weight loss.
There is evidence to suggest a very low carb diet may be effective for weight loss for overweight and obese adults over the short-term.9,10 However, current research concludes that a low carb diet is not more effective in achieving weight loss in the long-term.10 Similar to many diets, it can be challenging to follow prescriptive and restrictive recommendations in the long-term and especially when carbohydrate-counting is involved! It is also recognised that the initial weight lost on a low carb diet may be linked to muscle loss (which is often undesirable) and water loss, rather than fat loss.2,11 Weight loss is likely to be maintained only when attitude and behaviours, and dietary and physical activity habits are realistic and sustainable.
The Australian Dietary Guidelines do not encourage inappropriate food restriction such as the low carb diet and research shows that significant weight loss is achievable with energy-controlled diets that are high in carbohydrate-containing foods such as cereals and legumes.1,7 Evidence suggests a balanced diet with a combination of increased physical activity and energy restriction is most effective for weight loss and maintenance of weight loss.7
What are the risks of following a low carb diet?
Drastically reducing carbohydrate and potentially excluding entire food groups, including many healthy foods, means that our body’s nutritional requirements may not be met. The low carb diet can lead to deficiencies in vitamins, minerals and fibre, and a high intake of saturated fat. This is particularly relevant based on the well established link between dietary saturated fat and cardiovascular disease.7 If a high protein diet is followed, the probable association between red meat and certain cancers is also a potential risk.7 Following the low carb diet can also be expensive, impractical and unachievable for many Australians. The low carb diet forces the body to use fat stores for energy. This process is utilised in the Atkin’s diet and releases a by-product called ketones. Ketones can cause serious health risks including metabolic changes, increase the body’s acidity, alter consciousness and coma.7,12 A diet low in carbohydrate can also lead to short-term complications such as nausea, fatigue and constipation. Long-term health risks may include constipation, osteoporosis, weight gain, dieting issues, high cholesterol, abdominal obesity and obesity-related disorders, and kidney problems.2 More research is needed to determine the safety of a long-term low carb diet.
If not low carbohydrate, then what?
The word diet is derived from the Latin diaeta, meaning manner of living. This is consistent with the reality that food provides much more than sustenance, and is a complex component of people’s lives tied to socialisation, tradition, culture and religion. It is important to remember, therefore, that there is no one-size fits all diet, that food habits must be enjoyed to be sustainable for long-term benefits, and the aim for dietary advice is to be tailored to the individual and their lifestyle.
The problem with fad diets is the prescriptive and restrictive nature that can make them less enjoyable, more difficult to follow, and more difficult to maintain any benefits. It must also be considered that people promoting such diets may have minimal scientific education and financial motivation.
The Australian Dietary Guidelines identify a probable association between eating three to five serves of mainly wholegrain grain/cereal foods per day and reduced risk of weight gain.7 So rather than excluding carbohydrate-containing foods, the focus should be choosing more nutritious, wholegrain options (wholemeal breads and pastas, brown rice and untoasted muesli) over refined options (white breads, white pasta, white rice, processed cereals, cakes, biscuits and lollies).
The key message regardless of whether a diet is low or high in carbohydrate is to follow a less processed and whole food diet rather than focus on specific nutrients such as carbohydrate, fat or protein. The evidence for healthy eating and disease prevention emphasises a diet consisting of mostly plant-based foods including fruits, vegetables, wholegrains, legumes, low-fat dairy products and lean meats, and limiting processed foods that contain added saturated fat, added sugar and added salt. Combined with daily physical activity and avoiding large portion sizes, this eating pattern is the cornerstone to healthy sustainable weight loss.
Seek expert nutrition advice from an Accredited Practising Dietitian for individual, tailored recommendations.
- Dietitians Association of Australia. Carbohydrate [Internet]. Deakin ACT: Dietitians Association of Australia. [cited Dec 5]. Available from: http://daa.asn.au/for-the-public/smart-eating-for-you/nutrition-a-z/carbohydrate/
- Better Health Channel. Weight loss and carbohydrates [Internet]. Better Health Channel; date unknown [updated 2014 May 20; cited 2014 Dec 18]. Available from: http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/f074414e7ff88027ca257721001ae6f9/d2819557b8779fa6ca2572330024867c?OpenDocument
- Kouris A. Food sources of nutrients. A ready reckoner of macronutrients, micronutrients and phytonutrients. 2nd ed. A/Prof. Antigone Kouris-Blazos; 2012. 8 p.
- National Health and Medical Research Council. Eat for health. Educator guide. Information for nutrition educators. [Internet]. Canberra ACT: National Health and Medical Research Council; 2013 [cited 2014 Dec 5]. Available from: http://www.eatforhealth.gov.au/sites/default/files/files/the_guidelines/n55b_eat_for_health_educators_guide.pdf
- Wahlqvist ML, editor. Food & nutrition. Food and health systems in Australia and New Zealand. 3rd ed. Crows Nest NSW: Allen & Unwin; 2011. p. 280-1
- National Health and Medical Research Council. Nutrient reference values for Australia and New Zealand including recommended dietary intakes [Internet]. Canberra ACT: National Health and Medical Research Council; 2006 [cited 2014 Dec 5]. Available from: https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n35.pdf
- National Health and Medical Research Council. Eat for health. Australian dietary guidelines. Providing the scientific evidence for healthier Australian diets. [Internet]. Canberra ACT: National Health and Medical Research Council; 2013 [cited 2014 Dec 5]. Available from: https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n55_australian_dietary_guidelines_130530.pdf
- Feinmann RD, Pogozelski WK, Astrup A, Bernstein RK, Fine EJ, Westman EC, Accurso A, Frassetto L, Gower BA, McFarlane SI, Nielsen JV, Krarup T, Saslow L, Roth KS, Vernon MC, Volek JS, Wilshire GB, Dahlqvist A, Sundberg R, Childers A, Morrison K, Manninen AH, Dashti HM. Dietary carbohydrate restriction as the first approach in diabetes management: Critical review and evidence base. Nutrition [Internet]. 2015 Jan [cited Dec 18];31(1):1-13. Available from: http://0-www.sciencedirect.com.alpha2.latrobe.edu.au/science/article/pii/S0899900714003323 doi:10.1016/j.nut.2014.06.011
- Thomas D, Elliott EJ, Baur L. Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database of Systematic Reviews [Internet]. 2007 [cited 2014 Dec 18]; (3). Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD005105.pub2/pdf
- Dietitians Association of Australia. DAA best practice guidelines for the treatment of overweight and obesity in adults [Internet]. Canberra ACT: Dietitians Association of Australia. 2012 Jan 25 – [cited 2014 Dec 27]. Available from: http://daa.asn.au/wp-content/uploads/2011/03/FINAL-DAA-obesity-guidelines-report-25th-January-2011-2.pdf
- Dietitians Association of Australia. Fad diets [Internet]. Dietitians Association of Australia. [Cited 2014 Dec 20]. Available from: http://daa.asn.au/for-the-public/smart-eating-for-you/nutrition-a-z/fad-diets/
- Better Health Channel. Diabetes type 1. [Internet]. Better Health Channel. [updated 2014 May 20; cited 2014 Dec 18]. Available from: http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/f074414e7ff88027ca257721001ae6f9/4fd626afab7f1d90ca25723300248408?OpenDocument