The Atkins diet is a popular weight loss plan based on eating fewer carbohydrates and more fatty foods - low-carbohydrate:high-fat (LCHF) diet.
What is the Atkins diet?
Dr Robert Atkins was an American heart doctor (cardiologist) who first described the diet. Normally our bodies use glycogen (stored carbohydrate) for energy, but the body uses fat stores for energy when the glycogen runs out. Dr Atkins read about a diet low in carbohydrates which could help the body switch to burning fat instead of glucose as fuel.
He tried it out to get to his own goal weight. He then wrote a book, Dr Atkins' Diet Revolution, about his nutritional plan, which was published in 1972. The diet really took off in popularity after Dr Atkins' New Diet Revolution was published in 2002. The new book developed the ideas set out in the first book.
What are the phases of the Atkins diet?
There is an initial phase 1 induction phase to the diet, lasting about two weeks. During this phase, protein foods such as meat and fish are eaten freely. Carbohydrates are restricted to 20 grams (or fewer) per day. If this is very difficult to manage, a higher intake could be the starting point, but weight loss will be slower. Recommended foods contain much more fat than most dieters are used to, including cheese and cream.
During the second (balancing) phase, the carbohydrate intake is gradually increased, and weight loss continues more gradually.
This is a 'fine tuning' phase when you are approaching your target weight. The carbohydrate intake may be increased and your weight loss will slow down even further.
This is the maintenance phase. When the target weight is reached, carbohydrate intake is gradually increased to find the point at which weight is comfortably maintained, and not increased. This eating plan should be followed indefinitely.
What can you eat on the Atkins diet?
You should build your meals around a high-fat protein source with plenty of low-carbohydrate vegetables and nuts. Include some healthy fats also.
- Meat: pork, beef, lamb, chicken, bacon.
- Fatty fish and seafood: salmon, trout, sardines, mackerel.
- Low-carbohydrate vegetables: kale, spinach, broccoli, asparagus, courgette and cucumber.
- Full-fat dairy: butter, cheese, cream, yoghurt.
- Nuts and seeds: almonds, macadamia, walnuts, sunflower seeds.
- Oils and fats: extra virgin olive oil, avocado, avocado oil, coconut oil.
Allowable drinks on the Atkins diet include:
- Water: water is always the preferred option.
- Coffee: coffee is high in antioxidants.
- Green tea: green tea is also high in antioxidants.
Alcohol is allowable, but should be very dry wines with little sugar (carbohydrate) in them. Avoid beer which is high in carbohydrates.
How many carbohydrates are allowed on the Atkins diet?
If the body does not have carbohydrates, insulin levels remain low and this triggers a process called ketosis. In ketosis, the body uses fat reserves to provide energy. In the original Atkins diet plan, carbohydrates were severely restricted in the initial diet phase and this led to rapid weight loss. More recent updates to the plan allow a small amount of carbohydrate in the diet, and weight loss is generally more gradual. It also means that extreme ketosis is less likely.
Does the Atkins diet work?
Many people have found low-carbohydrate:high-fat (LCHF) diets such as the Atkins diet an effective way of weight loss and weight management. This may be because of the induction of ketosis, as described by Atkins. However, since most of our energy intake usually comes from carbohydrates, restricting them may simply have the effect of reducing overall energy intake. Also, high-protein foods increase the feeling of fullness after eating (satiety), so that may reduce hunger pangs and help to reduce weight gain.
Several studies comparing the outcomes of low-fat and low-carbohydrate diets concluded that both are effective for those who are able to stick to the diet plan.
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Is the Atkins diet safe?
While you may lose weight and experience other metabolic changes, the Atkins diet can also result in ketosis, particularly in the early phase of the diet. The mild dietary ketosis induced by eating a low-carbohydrate diet should not be confused with the dangerous condition of ketoacidosis. . However, mild ketosis during the initial phase of the Atkins diet can cause some symptoms such as:
Some people have found that a low-carbohydrate diet can result in depression, although this may be offset by the effective weight loss.
Increased saturated fat
There have been some concerns that a high meat intake might increase the body's levels of saturated fat. There were concerns that high-fat low-carbohydrate diets would result in an increased risk of obesity, heart disease, stroke and diabetes; however, long-term studies suggest the reverse is true..
Low levels of fibre
Other questions concern the low levels of fibre consumed in a low-carbohydrate diet. Fibre is necessary to keep our bowels moving healthily. A diet low in fibre may lead to an increased risk of developing bowel cancer. Fruits and vegetables are carbohydrate-containing foods which are restricted particularly in the initial phase of the Atkins diet.
One study found that a diet high in protein and low in carbohydrate affected the balance of the 'friendly' bacteria in the gut. This could have an effect on the health of the colon (the lower part of the bowel, or 'large intestine').
Other concerns which have been raised include a possible increase in non-alcoholic fatty liver disease or kidney stones, especially in people who stick to the diet for a long time. One research paper showed that following a high-protein diet could further damage kidneys if they were already failing, or at risk of damage. There was, however, no risk to healthy kidneys.
Another criticism of the diet is that it can be quite expensive to follow. A meat-based diet costs more than one based on starchy vegetables and foods..
Is the Atkins diet safe for people with diabetes?
Ketoacidosis can be life-threatening in those with diabetes, who are not able to control the levels of the chemical (hormone) called insulin and glucose in their bodies.
Is the Atkins diet safe long-term?
There are concerns that people who stick to a low-carbohydrate diet for a long time may miss out on vitamins and other important nutrients in fruit and vegetables. There seems to be no clear advantage of one over the other in terms of short- or long-term effectiveness. The health risks and benefits are similar.
Benefits of the Atkins diet
High-protein ketogenic diets are used in the management of some medical conditions. Ketogenic diets have been used to treat epilepsy since about 1920. However, today they are mainly used for children with difficult-to-control epilepsy. Recent studies have confirmed its effectiveness for this purpose, but questions have been raised about its long-term effects on cardiovascular health. The use of this diet in children with epilepsy should only be tried under guidance from a doctor.
Research is continuing into whether low-carbohydrate diets may be helpful for people with Alzheimer's disease and Parkinson's disease.
A low-carbohydrate diet may also benefit those with disorders such as type 2 diabetes, metabolic syndrome and polycystic ovary syndrome. In these conditions one of the problems is the way the body processes sugars and the chemical (hormone) called insulin. Often they find losing weight by following a traditional low-fat diet particularly difficult.
The Atkins diet seems to be an effective way of losing weight for many people. However, eating a low-carbohydrate and high-protein diet has many different effects on different systems in the body. These are not fully understood and are still being investigated.
What other options are there to lose weight?
Other types of diet are available - for example:
There are other ways of changing your diet and altering your lifestyle to help you lose weight, such as increasing your physical activity.
You may find other leaflets in this series helpful, including:
Further reading and references
Johnston BC, Kanters S, Bandayrel K, et al; Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014 Sep 3312(9):923-33. doi: 10.1001/jama.2014.10397.
Hansen CD, Gram-Kampmann EM, Hansen JK, et al; Effect of Calorie-Unrestricted Low-Carbohydrate, High-Fat Diet Versus High-Carbohydrate, Low-Fat Diet on Type 2 Diabetes and Nonalcoholic Fatty Liver Disease : A Randomized Controlled Trial. Ann Intern Med. 2023 Jan176(1):10-21. doi: 10.7326/M22-1787. Epub 2022 Dec 13.
Noakes TD, Windt J; Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review. Br J Sports Med. 2017 Jan51(2):133-139. doi: 10.1136/bjsports-2016-096491.
Martin K, Jackson CF, Levy RG, et al; Ketogenic diet and other dietary treatments for epilepsy. Cochrane Database Syst Rev. 2016 Feb 92:CD001903. doi: 10.1002/14651858.CD001903.pub3.
Gratz SW, Hazim S, Richardson AJ, et al; Dietary carbohydrate rather than protein intake drives colonic microbial fermentation during weight loss. Eur J Nutr. 2018 Feb 20. pii: 10.1007/s00394-018-1629-x. doi: 10.1007/s00394-018-1629-x.
Burke LM; Ketogenic low-CHO, high-fat diet: the future of elite endurance sport? J Physiol. 2021 Feb599(3):819-843. doi: 10.1113/JP278928. Epub 2020 Jun 10.