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What is the Sirtfood diet?

Launched in 2016, the Sirtfood diet remains a hot topic and involves followers adopting a diet rich in ‘sirtfoods’. According to the diet's founders, these special foods contain natural plant compounds (such as polyphenols) that work by activating a group of seven signalling proteins found in the body, called sirtuins.

Sirtuins are believed to help your body burn stored fat in a similar way to that of fasting and exercise. They also protect cells in the body from dying when under stress and are thought to regulate inflammation, make our bodies more energy efficient and slow down the aging process.

Discover all you need to know about diets, read more about the dopamine diet and detox diet. Also check out the top sirtfood diet recipes.

What is the Sirtfood diet?

How does the Sirtfood diet work?

It's thought that sirtuins influence the body’s ability to burn fat and boost metabolism resulting, it is claimed, in a 7lb (3kg) weight loss a week, while still maintaining muscle. However, some experts believe this is unlikely to be solely fat loss, but may instead reflect changes in glycogen stores from skeletal muscle and the liver.

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How do you follow a Sirtfood diet?

The diet lasts three weeks in total and is divided into two phases:

Phase 1 (7 days)

Days 1-3 – calories are restricted to 1000kcal per day. This involves a daily intake of three sirtfood green juices and one meal rich in sirtfoods. The ingredients in the juices include kale, celery, rocket, parsley, green tea and lemon. Examples of meals might be turkey escalope with sage, capers & parsley; chicken & kale curry or prawn stir-fry with buckwheat noodles.

Days 4-7 – calorie intake is increased to 1500kcal per day and comprises two sirtfood green juices and two sirtfood-rich meals.

Phase 2 (14 days)

This phase is known as the maintenance phase where steady weight loss occurs. During this phase you have one sirtfood green juice and three balanced meals, rich in sirtfoods.

Kale leaves in a colander

What can I eat on the Sirtfood diet?

The good news is there are a large number of foods that contain polyphenols, with the most common including:

  • Green tea
  • Dark chocolate (at least 85 per cent cocoa)
  • Apples
  • Citrus fruits
  • Parsley
  • Turmeric
  • Kale
  • Celery
  • Red onion
  • Blueberries
  • Soy
  • Capers
  • Flaxseeds
  • Nuts including hazelnuts
  • Red wine

What foods should I limit on the Sirtfood diet?

Although the diet promotes healthy foods, rich in polyphenols, it's relatively restrictive in both your food choice and daily calories, especially during the initial stages. The foods you are advised to avoid include refined and processed foods that lack the beneficial natural compounds (polyphenols), such as white bread, pastries, cakes and confectionery as well as sugary drinks.

Will I lose weight following the Sirtfood diet?

The authors believe the diet offers a sustainable and realistic way to lose weight, however, their claims are not, to date, backed by robust scientific evidence. This may in part be because of the complexities of evaluating the effects of sirtuins, for example, levels found in the blood do not reflect the activity in the cells and until reference ranges are established, blood levels of sirtuins can’t be used as a valid biomarker.

The authors also suggest that focusing on weight loss is not what the diet is all about – it’s designed to be about eating the best foods nature has to offer. In the long term, it's recommended that you eat three balanced sirtfood-rich meals a day, along with one sirtfood green juice. This is believed to provide health benefits such as supporting energy and mood and potentially reducing the risk of chronic disease.

Feet on scales

Is the Sirtfood diet healthy? A nutritionist’s view…

The initial phases of the diet are restrictive – aiming to have 1000kcal per day for three consecutive days is difficult and may be an unrealistic ask for some people. This phase of the diet also involves drinking juice and, during phase one, quantities exceed the daily guidelines.

In the list of permitted foods, the majority are plenty of nutrient-dense options. However, the list does omit other healthful foods, such as dairy, which means the diet may be lacking in some essential nutrients including iodine and calcium.

In terms of weight loss and boosting metabolism, people may experience weight loss on the scales but this is likely to be down to a loss of stored glycogen and fluid. Burning and losing fat takes time so it's unlikely this weight loss will be sustainable. The diet offers limited long-term guidance, which means followers returning to their original eating habits after the two phases of the diet are likely to re-gain the weight they lost.

If you are considering the Sirtfood diet you should be aware that it does not comply with the weight loss guidelines recommended by the NHS, which includes a reduction in daily calorie intake by around 600kcal. The NHS also recommends a balanced and varied diet including all five food groups – fruit and vegetables; starchy carbs; protein, dairy or fortified alternatives and a small intake of fats and oils.

Should I follow a Sirtfood diet?

Slow and steady is key when it comes to weight loss. In order to lose weight and keep it off, it's best to increase your activity levels, create a calorie deficit, consider your meal timings and ensure an overnight fast. Eating balanced regular meals made up of low-GI foods, lean protein, fruit and vegetables and keeping well hydrated is the most sustainable way to lose weight.

Weight loss and good health can be achieved by following a healthy, balanced diet. Our nutritionist-approved plan helps you find your perfect portion size, guideline daily amounts and nutritionally balanced breakfasts, lunches, dinners and snacks.

Please note: if you're 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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This page was last reviewed on 29 December 2023 by Kerry Torrens.

Emer Delaney BSc (Hons), RD has an honours degree in Human Nutrition and Dietetics from the University of Ulster. She has worked as a dietitian in some of London's top teaching hospitals and is currently based in Chelsea.

Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.

All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.


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