How does the Atkins diet work?
The Atkins diet is similar to a ketogenic diet as both emphasise the consumption of fat and protein but severely restrict the body’s favoured energy source, carbohydrates. Ketogenic diets essentially force the body to switch from burning carbohydrates for energy to burning fat. This often has the desirable effect of weight loss, though high levels of ketones in the body can be problematic and may lead to a secondary condition known as ketoacidosis.
The theory behind a low-carb diet is that by limiting carbohydrates you help the body burn fat instead. Over time, some argue that this contributes to higher energy levels throughout the day and potentially allows you to reach weight loss and weight maintenance goals.
How to follow the Atkins diet
There are three Atkins plans designed to help dieters reach their goals:
- Atkins20 – aim for 20g ‘net carbs’ per day, with 12-15g coming from vegetables.
- Atkins40 – allows a little more flexibility, this permits 40g ‘net carbs’ per day, with 12-15g coming from vegetables
- Atkins100 – for those who want to maintain weight loss or want slow, steady weight loss, this plan permits 100g ‘net carbs’ per day, with 12-15g coming from vegetables.
There are four phases to Atkins:
1. Induction phase
This is designed to jumpstart your weight loss and change the way your body uses macro-nutrients for energy. Carbs are restricted to an average of 20g net carbs per day which encourages the body to use fat as its primary source of energy.
How long you stay in this phase depends on how much weight you have to lose, but on average it is about 2 weeks.
2. Second stage
Focuses on continued weight loss, whilst gradually re-introducing some carbohydrates back into your diet whilst avoiding weight gain.
3. Pre-maintenance stage
Continues to re-introduce carbs back into the diet, with the main objectives for dieters being to lose the last 10 pounds slowly, test their tolerance for previously forbidden foods and maintain previous weight loss. Once you’ve maintained your goal weight for a month, you’re ready to move onto stage four…
4. Lifelong phase
Billed simply as maintenance – Atkins suggests that by now you should have discovered how many carbohydrates you can include in your diet without regaining weight. You should also not be prone to cravings or undue hunger.
What foods to eat
The specific foods will depend on which phase of the chosen plan you are following. However, foods low in carbs such as fats and oils, fish, poultry, meat and eggs are permitted as well as diet soda, broth, tea and coffee.
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A certain amount of ‘foundation’ vegetables are advised (the equivalent of 12-15g net carbs per day). These include spinach, lettuce, watercress and sprouts.
In order to achieve your 5-a-day, followers of the Atkins diet need to understand which fruit and veg are low in carbs. Good choices of non-starchy veg are courgette, cucumber and leafy greens like spinach. Low carb fruits include avocado and olives. Eating a wide range of fruit and veg not only allows us to get plenty of vitamins and fibre but also means we benefit from protective plant compounds like flavonoids and carotenoids which may help fight heart disease, certain cancers and may slow the signs of aging.
What foods to avoid
Again, the foods to avoid depend on the plan you’re following and phase you’re in. Typical foods to be avoided include starchy vegetables like corn and potatoes; fruits with a high sugar content such as pineapple, mango and banana; baked goods such as biscuits and cakes as well as refined carbs such as white bread, pasta and rice as well as sugary drinks.
During the induction phase some foods like carrots, apples and legumes are also not included.
What are ‘net carbs’?
Atkins suggests that ‘net carbs’ reflect the grams of carbs that impact your blood sugar levels. When following the Atkins plan you are required to calculate the ‘net carbs’ in your diet.
What’s the evidence for the Atkins diet?
Studies examining the effectiveness of low carb diets, like Atkins, report faster weight loss at 6 months but no difference after 12 months to that achieved from a low fat, calorie restricted regime. There are some additional benefits, including minimising food cravings, especially those for sweet foods, and improving blood sugar balance.
The downsides of low-carb diets, however, include feelings of fatigue and nausea, possible electrolyte imbalances and the fact that it may hinder exercise performance and activity levels.
Studies also suggest that following a low-carb diet, like Atkins, may alter your gut microbiota, this may have a detrimental effect on the production of short chain fatty acids (SCFAs) which play a protective role both in the gut and for your general health.
Is the Atkins diet healthy? Our nutritionist’s view
The Atkins diet comes from the idea that carbs are responsible for weight gain and that by eating more fat and protein we can switch on the “satiated” trigger, which helps us control our appetite. For this reason, strict limits are put on carbs especially during the initial weight loss stage, but unlike most other diets there are no restrictions on the amount of fat you eat. Unsurprisingly, it’s during this initial phase that most weight loss is achieved, although much of this is likely to be due to the loss of glycogen stores combined with water, this weight is easily re-gained once carbs are re-introduced.
The plan encourages dieters to cut out processed, refined carbs as well as alcohol but allows the inclusion of red meat, butter, cream and cheese. The only fat Atkins suggests you avoid are the man-made trans fats typically found in spreads and processed foods. These trans fats have been linked to clogged arteries and an increased risk of heart disease and stroke.
Enjoying some fat in a healthy, balanced diet is important because not only does it help promote our absorption of fat-soluble vitamins like vitamin A, D, E and K, certain fats are also essential to health. More recent evidence supports the idea that saturated fat in dairy foods may be less harmful than we once thought. However, although Atkins places no limit on saturates, public health advice remains that we should limit our consumption to 20g of saturates daily.
Most health professionals believe that cutting out major food groups, such as carbs, is detrimental to long-term health. Critics of high-protein diets fear it may have an adverse effect on bone health, as well as renal function for those with an existing kidney condition. Currently, we don’t know the risks of following a low-carb diet over the longer term because most studies have lasted two years or less. Therefore, more studies are needed to assess changes in nutritional status, body composition and cardiovascular risk factors.
Does the Atkins diet work?
In the short-term, weight loss is achieved and at a relatively fast rate. Over the longer term there is no evidence that Atkins is any more effective than a standard calorie restricted weight loss plan.
Who shouldn’t follow the Atkins diet?
Diabetics are at risk of complications if they attempt to follow a strict low-carb diet. Anyone with a blood sugar management issue should discuss the potential implications with their GP before embarking on such a regime.
Similarly, anyone who meets one of these criteria:
- has a kidney and / or liver disease or a family history of such;
- is under 18 years old or elderly;
- has a pre-existing medical condition;
- are pregnant or breastfeeding;
- have or are recovering from an eating disorder
- or are on prescribed medication including (but not restricted to) insulin, oral diabetic meds or diuretics.
Please note, if you are considering attempting any form of diet please consult your GP first to ensure you can do so without risk to health.
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If you want to read more about net carbs and the Atkins diet in more detail you can do so at atkins.com
This article was last reviewed on 25th October 2023 by registered nutritionist Kerry Torrens.
A nutritionist (MBANT) Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).
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