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Noom, sirtfood, f-factor - our dietitians review the latest diet trends

No matter your health goal, there’s always a new diet promising to be the ‘quick fix’ that’ll help you achieve your wellness dreams. Our dietitians investigated three of the latest diets to determine whether any are based on reliable evidence to actually deliver what they claim while ensuring overall good health and sustainable weight loss.

Sirtfood diet

The Sirtfood diet recently hit the headlines as the regime behind UK singer Adele’s dramatic weight loss transformation. Created by Adam Goggins and Glen Matten, the Sirtfood diet promises to activate ‘sirtuins’ – enzymes that help dieters lose weight “while eating chocolate and drinking wine”. But is there any truth to their claims?

Some research has found that sirtuins can reap various benefits, from protecting cells in your body from inflammation to helping with metabolism and increasing lifespan. The idea is that eating specific ‘sirtuin’ foods (or sirtfoods) which contain natural plant compounds will increase the level of sirtuin enzymes in the body. However, the evidence surrounding their benefits is unclear and there’s no guarantee the diet will actually trigger sirtuin genes, aka ‘skinny’ genes.

The diet combines calorie restriction with a heavy focus on consuming specific sirtfoods, and is based around two ‘phases’:

  • Phase 1 is the ‘hyper-success’ phase. It is seven days long, with days 1-3 consisting of three sirtfood green juices and one sirtfood meal, totalling just 1,000 calories. On days 4-7 calorie intake is upped to 1,500 calories, with two green juices and two meals per day.
  • Phase 2 is the ‘maintenance’ phase and lasts two weeks. Diet-goers are permitted three sirtfood-rich meals each day in addition to one special green juice.

The two phases can be repeated whenever weight loss is desired. Once the phases have ended, the diet focuses more on what you eat, rather than how much and diet-goers are encouraged to continue including sirtfoods and the diet’s signature green juice in their meals.
What counts as a sirtfood?
Some of the top 20 foods on the sirtfood green list include green tea, apples, citrus fruits, parsley, turmeric, kale, blueberries, capers, dark chocolate and red wine. Limiting your diet to only sirtfoods is very restrictive and unnecessary as there are many nutritious foods the diet doesn’t factor in, including fibre-rich, nutrient-packed wholegrains, legumes, nuts and seeds. Eating a greater variety of these foods is more likely to ensure all nutrients are covered. 
Should you try it?
There is no scientific evidence that ‘skinny genes’ are activated for weight loss or that sirtfoods are more beneficial for weight loss than other plant foods. Instead there is plenty of evidence that eating a wide variety of high fibre plant foods helps with overall good health and sustained weight loss.

The Sirtfood diet is highly prescriptive and measures success only in weight loss. In addition, while incorporating sirtfoods into your diet isn’t going to hurt, there’s no evidence that they are any more special than other fruit and vegetables. There are also no specific robust clinical trials on this diet. Therefore we wouldn’t recommend the Sirtfood diet. Instead it is better to consider your overall health goals and make realistic lifestyle changes that you can sustain over the long term. Talking with your GP or dietitian can help you achieve this.  

Noom diet

You may have seen the Noom diet gracing your social feeds this year. Touted as a ‘diet with a difference’, the Noom diet is an app focused on helping people lose weight through psychology. Created in 2008 by businessman Saeju Jeong and software engineer Artem Petakov with the help of dietitians, the Noom diet was developed with an emphasis on psychology as much as nutrition – it aims to help people change behaviours and reevaluate the thought processes behind food decisions. It’s said to have had more than 45 million followers.
How the app works
After downloading the app, Noom diet followers log their weight loss goals, activity levels and food intake in order to keep track of their calorie intake for the day. Daily calorie targets adjust depending on the information logged. Being part of a support group via the app increases chances of keeping the weight off.

Foods are colour-coded, with diet-goers urged to eat according to a colour-coded system:
  • 30% ‘green’ foods – those with the lowest amount of calories per mass, including wholegrains, fruits and vegetables.
  • 40% ‘yellow’ foods – those higher in calories such as beans, low-fat cheeses, yoghurt and low-fat types of meat.
  • 25% or less ‘red’ foods – the most calorie-dense foods, including red meat, juice, nuts, chocolate and pizza.
Should you try it?
Overall, Noom may be a helpful tool for some people. On the plus side, it promotes lower calorie intake and nutrient dense whole foods, without eliminating any food groups. The app can also help people identify some of their behaviour triggers for unhealthy eating, and reinforce healthy eating habits.

However, Noom can be expensive because of the additional coaching, tracking and educational features. It also advocates closely monitoring everything you eat and drink, which can be a useful motivator, but monitoring can be difficult to sustain in the long term.

It’s also important to note there is no evidence to date to show that Noom is more effective than following general healthy eating advice. The Australian Guide to Healthy Eating focuses on mostly nutrient-dense lower calorie foods while minimising lower nutrient, calorie-dense foods, with information freely available at eatforhealth.gov.au.   

F-Factor diet

The F-Factor diet has been around since 2007, but has entered the spotlight recently with the media sharing people’s experiences with the diet. Created by New York registered dietitian Tanya Zuckerbrot, the diet heroes are lean protein and high fibre carbs – the diet’s emphasis on fibre being its namesake (the ‘F’ in ‘F-Factor’ stands for ‘fibre’).

The F-Factor diet is broken down into steps:
  • Step 1 lasts for 2 weeks and allows at least 35 grams of fibre, and less than 35 grams of carbohydrates per day.
  • Step 2 shifts to 35 grams of fibre and 75 grams of carbohydrates per day, and lasts until the weight loss goal is achieved.
  • Step 3 – the ‘maintenance’ phase – allows 35 grams of fibre, but less than 125 grams of carbohydrates per day.


Fibre and wholegrains

Fibre is key for good health. It’s recommended that Aussie adults consume at least 25-30 grams of fibre each day. In fact the Australian Dietary Guidelines recommend that we eat wholegrain and high fibre grain foods most of the time, as they contain a range of protective components such as phytonutrients, thought to play an important role in the prevention of disease.

Should you try it?

We love a focus on fibre. It’s a key beneficial componment of a plant based diet and essential for gut health. However, this diet seems a little contradictory, focusing on high fibre foods (which are typically high carb foods) while advocating minimising carbs.

It’s important to consume enough energy and adequate nutrients without excluding one or two food groups. If you limit the amount of carbs you eat in a day, you may not get enough of the different fibre types. By choosing quality carbs most of the time, you will get a diversity of those important fibres.

This means eating a variety of high fibre wholegrains, legumes, fruits, nuts/seeds, veggies. These foods help to ensure you are getting enough of each fibre type – insoluble, soluble, and resistant starch. They also provide quality carbs, but minimise refined carbs. They help to lower blood pressure, and reduce risk of heart problems, diabetes and obesity. 

A word of warning on high fibre diets – be sure to increase your intake of fibre gradually as too much too quickly could mean excessive bloating and gas.

So what’s our overall verdict?

While it may be tempting to opt for diets that promise quick weight loss, the key to making sustainable lifestyle changes is finding a healthy, balanced diet that works for you over the long term. We recommend a dietary pattern that is high in plant foods, like fruits, veggies, wholegrains, legumes, soy, nuts and seeds. If you are wanting to make some dietary changes for a healthier you, talk to a dietitian or registered nutritionist who will be able to provide you with dietary advice that is specific to your needs.