Are you religiously following a diet myth? Diet rules dispelled by science

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By The Gut Health Doctor Team

Dr Megan Rossi in a lab looking through a microscope

Many of us have fallen prey to food fads and the odd diet myth. They vary from harmless misconceptions that have been around for decades to unhelpful (if not downright dangerous) dieting ‘rules’. Unfortunately, lots of people base their meals on these outdated mantras that the science simply does not back up. 

Today, we’re looking at 7 of these misleading myths to empower you to find a new joy in mealtimes, and break free from these outdated food rules that don’t lead to their promised result…  

Our diet rules debunking guide

Diet myth no.1: ‘Don’t drink with your meal’

Photo of someone with a grey jumper sleeve holding a glass of water outdoors to reflect the diet myth of drinking with food

MythYou should take a 30-minute break between eating your meal and having a drink.

Fact: Drinking water with meals may actually be a good idea, particularly if you are a fast easer.

This myth has been around for decades and is based on the belief that drinking anything, even water, with meals will dilute your digestive enzymes. But your body is much smarter than that! While it’s possible that drinking might momentarily dilute the concentration of stomach enzymes, there are sensors in the stomach to ensure that as many enzymes as you need to digest a meal are produced.

In fact, drinking water with meals is a good idea if you eat too fast or too much, as it can slow mealtimes down. This in turn gives your digestive enzymes and appetite hormones more time to regulate and therefore can promote better digestion and can reduce the likelihood of overeating.

Diet myth no.2: ‘You need to cut out carbs to lose weight’

Photo of a spread of wholegrains and healthy food on a table including brown bread and wholegrain crackers to dispel diet myth of avoiding carbs and gluten

Myth: Carbohydrates raise blood sugar levels and cause weight gain.

Fact: For most of us, good-quality carbohydrates are a valuable addition to our diet.

Many unrefined sources of carbohydrates (e.g. quinoa, barley and oats) are a good source of fibre (we need at least 30g a day) and a 2019 review by Tufts University in the U.S.A, showed that a higher intake of wholegrains may actually lower the risk of weight gain. Carbs have certainly picked up a bad reputation in recent years, but cutting them out can have a negative impact on our gut microbes. In fact, fibre is actually classified as a type of carbohydrate!

Of course, highly processed breads, cakes and biscuits are not necessarily helpful but wholegrains such as quinoa and rye, legumes such as chickpeas and lentils, and other wholefood plant-based carbs make for a healthy gut.

Diet myth no.3: ‘Fruit is just full of sugar’

Photo of a bowl of fruit on a wooden table from a top angle, including blackberries, kiwi slices, blueberries, orange segments and raspberries to reflect diet myth of avoiding fruit

Myth: Fruit is just sugar and plays a limited part part in a healthy diet.

Fact: Fruit is full of important phytochemicals and dietary fibres, which help counter blood sugar spikes seen with added sugars, such as agave, honey and standard table sugar. Fruit is also a great addition to your diet as it is packed with vitamins and other plant- based compounds (called phytochemicals), which are good for our gut microbes and nourish the gut-brain axis. And while we’re here, some people believe that fruit has to be eaten on an empty stomach, as otherwise it ‘slows’ digestion but, again, there is no scientific foundation for this.

We generally recommend two pieces of fruit a day, with the goal of having at least five different types across the week. The more diverse your fruit intake, the more varied phytochemicals for your gut microbes to enjoy.

Diet myth no.4: ‘Processed food is to be avoided’

Photo of a shelf including 9 tins of food, including canned tomatoes, sweetcorn and peas. Some of the cans are open and some are closed. To demonstrate diet myth of processed foods

Myth: All processed foods are unhealthy.

Fact: The definition of processed food is simply any food altered from its natural state.

Of course, excessive consumption of ultra-processed foods containing high levels of fat, salt, sugar and additives can affect our gut microbes, encourage over-eating (because of their low fibre content among other potential mechanisms) and has even been linked with poor mental health. However, this doesn’t apply to all processed foods. Our busy lives mean we can’t always make everything from scratch, and even virtuous Greek yoghurt is considered processed by definition. 

Rather than rejecting anything ‘processed’, learn how to read labels (check out our series here). Ingredients are listed by weight, with the largest amount first, so check out the first four foods listed. This way you can focus instead on buying foods with wholesome ingredients you recognise, rather than refined alternatives ladened with a long list of additives.

Diet myth no.5: ‘Fresh is best’

Photo of a woman with her hair up opening a freezer door in a shop with frozen vegetables in the background to reflect diet myth of fresh food is better for you

Myth: It’s only worth eating fresh fruit and vegetables otherwise you won’t get the benefit.

Fact: Tinned or frozen food sometimes contains more nutrients than the fresh produce

A study by Pennsylvania State University in the U.S.A found that fresh spinach lost nearly half its folate (a B vitamin) after eight days in the fridge(1). However, frozen vegetables lose only a fraction of their B vitamins when blanched before freezing, and are otherwise bursting with goodness. Similarly, there is a slight reduction in nutrients when veg is heated during the canning process, but the vast majority are retained, just ensure it’s not canned in brine (i.e. salt).

Using tinned or frozen foods, alongside fresh, can help you build more plant variety into your meals more cost-effectively, and with less risk of waste. 

Diet myth no.6: ‘Nothing beats a homecooked meal’

Photo of a someone kneading dough on a table covered in flour and a rolling pin in the background to reflect diet myth of homecooked food is better for you

Myth: Homemade food is better for you than shop bought.

Fact: Don’t presume what comes out of your kitchen is automatically healthier.

Ok, a homemade casserole is likely to be better for you than a ready meal, but that doesn’t mean all homemade food is good for you — or healthier than a shop-bought product. For example, a homemade biscuit with 50% butter and 30% sugar is arguably worse for you than an oat-based, mass-produced biscuit such as a Hobnob, which is made of almost 40% oats.

Diet myth no.7: ‘It’s important to count your calories’

Photo of a green calculator, measuring table and some vegetables and fruit on a grey top table to reflect calorie counting

Myth: The number of calories in your food is an accurate way to watch what you eat

Fact: Calorie counting doesn’t account for what actually happens in your body.

And last but by no means least, this diet rule is one that so many people are religious about — but it comes with many scientific flaws. Firstly, the calorie count on labels is often inaccurate as it’s based on what happens in a laboratory, not what goes on in your body. Secondly, not all calories are created equal when it comes to digesting them. For instance, a 2010 study found that digesting a processed meal used nearly 50% fewer calories than the amount used to digest a whole-food meal (i.e. one based on veg, nuts and wholegrains).

Illustration of a woman picking out a grain out of a tapestry of different types of plants to show plant diversity


Because there’s so much misinformation out there, it’s really tricky to know what’s best when it comes to eating. The main thing is to try and centre your meals around whole plant foods that have been minimally processed (so no to those ultra-processed vegan burgers and yes to homemade chickpea burgers), as this will ensure your diet is more nutrient dense and naturally curb your appetite for less nourishing foods. And if you’re feeling anxious, always remember that if you’re cooking with an inclusive, diverse and joyful approach to food, you’re on the right track. Still confused? You can always talk through an optimal, personalised approach to eating for you with one of our specialist registered dietitians at The Gut Health Clinic.


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