3 New Year Diets Debunked by a Dietitian

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New year new me! But are these diets actually healthy? And sure we hear a lot about them online but does that already mean they are actually tried and tested to work according to the evidence? Let’s check them out.

1. Keto Diet

The keto diet is a very low carb, moderate protein, and high fat diet which involves replacing carbohydrates as the body’s primary energy source placing the body into a metabolic state known as ‘ketosis’. In ketosis, fat is being used as fuel instead of glycogen and glucose

Where did it come from?

The keto diet was originally created for children with epilepsy as a keto diet has been shown to reduce seizures in children. It is very appealing for fat loss because of the ‘fat burning state’ and evidence has been shown to improve blood glucose control.

How does the weight loss work?

It is also appealing because of the rapid weight loss at the start of the diet however this is mainly water weight as reducing carbohydrates leads to reduced glycogen stores in the liver and muscles. Each gram of glycogen can hold 3 grams of water.

Weight loss is not mainly due to reducing carbohydrates but when we eat less carbohydrates or set ‘limits’ we are being much more wary of hyper-palatable carbohydrate-rich foods such as donuts and cakes which are high in energy and consuming more protein which is very filling helps with this.

Evidence shows that if you are eating in an energy deficit (eating less than your body uses in a day) whether you are in ketosis or not, you will lose weight.


It is not a recommended diet unless you are a child with epilepsy as eating a very low carb diet can reduce vitamin and mineral consumption by reducing fruits and vegetables too and it has been shown that people on keto diets struggle with regular constipation and the ‘keto flu’.

You may be unnecessarily restricting foods you love like cakes and donuts for example as you may lose weight even with a non-keto diet as long as you are consuming less energy than your body requires.

2. Vegan Diet

A vegan diet is a way of eating where no animal product (meat) or byproducts (eggs or dairy) of animals are consumed. It is a diet that focused wholly on plant foods.

How does the weight loss work?

Consuming more plant foods means you will be consuming much more fibre in your diet. Fibre is very beneficial for keeping us full, improving stools, reducing blood pressure, improving blood sugar control, and reducing LDL (bad) cholesterol. – Whilst fibre is beneficial, consuming excess fibre when you IBS or an IBD flare-up may worsen symptoms but this doesn’t mean you cannot follow a vegan diet.

However, just because a food is vegan does not mean it will guarantee weight loss. Weight loss is dictated by whether you are eating in an energy deficit (consuming less calories than you body uses). Vegan diets contain hyper-palatable foods such as vegan cookies, vegan cakes, and more.

If you are focusing on whole, plant based foods such as hummous, tofu, pulses, herbs, fruits and vegetables for example, then you may maximise the benefits of a vegan diet for your goals.

It is important to note that whether you choose to follow this diet for health or ethics, there are certain nutrients that are difficult to obtain in a vegan diet.

Make sure you focus on supplementing vitamin B12 (as there is very few vegan sources of this on a vegan diet), calcium, vitamin D, iodine, selenium, iron (as vegans are at a much higher risk of anaemia), and may need to also focus on protein as plant-based sources are less absorbed than meat-based sources.


The vegan diet is a great diet if you choose weight loss, but once again, vegan diet or not, the key focus is on eating less than your body requires for fat loss. Fibre is a key component on making weight loss much easier because it is very satiating which is found in fruits, vegetables, pulses, and most meat alternatives.

See the Vegan Society for more info

3. Intermittent Fasting

Intermittent fasting is not a diet but a way of timing when you eat instead of what you eat. The most popular ways of doing intermittent fasting is the 5:2 and the 8:16.

The 5:2 diet works around the principle that you eat a healthy balanced diet five days a week and then you fast for the remaining two days. You don’t have to choose consecutive days.

On fasting days the calorie allowance is 500 for women and 600 for men, with recommended foods being lean sources of protein, vegetables and juices.

The 8:16 plan works slightly differently in that you restrict your eating time to an eight-hour window – for example: from 9 am until 5 pm – and fast the rest of the time.

How does the weight loss work?

When you are fasting (not eating) you are essentially using your body’s stored energy (glycogen) and fat stores but you can still gain weight if you are not in a caloric deficit (once gain, eating less calories than you use!)


The common way of intermittent fasting is the 8:16 and most people would have 2 meals a day. having 2 meals a day would make you less likely to eat less overall in the day. You may even gain weight even if you have been fasting for most of the day if you eat more calories than you burn.


The best diet is the diet that you enjoy. One that is not unnecessarily restrictive and one that you can see yourself that works best for your lifestyle, culture, medical condition, and mental health.


Key focus on what makes a diet easy for weight loss if that is your goal:

  • Focus on increasing your fibre intake to 30g a day
  • Consume increased amounts of protein
  • Consume at least 5 portions of fruits and vegetables a day
  • Reduce ‘drinking’ your calories
  • Include foods you enjoy in moderation

If your diet is negatively affecting your mental health and is seen as ‘something that has to be endured’ you’re doing it wrong. – And that is coming from a dietitian. Those are the new year diets debunked!

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