Diet expert Dr Michael Mosley reveals why your favourite breakfast foods could be doing you more harm than good

, wrote on his blog that it can be "confusing" to know which foods are best to buy at the supermarket when so many have clever “healthy” marketing.

This is especially the case when it comes to cereal, granola, porridge and yoghurt - four morning staples.

The diet guru said: “It can often be overwhelming with the amount of options when it comes to the cereal aisle.

“As a result, most opt for the boxes that look the healthiest.

"However, even cereal boxes with a four-star health rating in Australia, for example, or mostly green boxes if you’re in the UK, can contain up to 23 per cent sugar. 

“Be cautious as even the ones with high fibre ingredients, like bran and oats, are still laden with sugar.”

“Healthy” breakfast cereals are one of the easiest traps to fall into, he added.

The best way to assess whether your cereal is good for you is to read the nutrition label and compare the levels of sugar, fat and calories in a serving compared to the daily recommended allowances.

These are:

• Sugar: 30g of “free/added sugar” a day for adults
• Saturated fat: 30g a day for men, 20g a day for women 
• Calories: 2,500 for men, 2,000 for women

Knowing these figures means you’ll be able to assess whether a small 45g bowl of cereal with 10g of sugar, and so on, is healthy or not.

“Granola falls into the same category,” Dr Mosley said. 

“Quite often considered to be a healthy option, shop-bought granola is incredibly high in sugars, carbohydrates and calories. 

“Not only this, the recommended serving size is considerably smaller than you may think with most brands recommending 40g, which is the equivalent of around three tablespoons.”

Most people eat more than the recommended 40 to 45g of cereal or granola, therefore having up to double the sugar, fat and calories than are written on the box.

“If you enjoy granola or cereal for breakfast, always check the ingredients and avoid any with dried fruits and chocolate chips,” says Dr Mosley.

The expert also said to avoid porridge sachets which require water.

He said: “You may as well be having three spoonfuls of sugar instead as some brands have an astonishing 16g of sugar per serving.

“Make it yourself from rolled oats and water, or whole milk, and you’ve got yourself a winning breakfast.”

ENERGY 'CRASH'

And lastly, low-fat products such as yoghurt should also be avoided, he added.

"Low fat products are stripped of their nutrients and often laden with additives and sugar," he said.

"This is to compensate for the flavour that gets removed in the process of making them fat free.

"Products high in sugar and low in fat will spike your glucose levels and leave you craving more as there is nothing to prolong the energy release."

Instead, people should opt for full-fat versions, such as Greek yoghurt, which is full of protein.

The doctor listed half a dozen other foods that people should be wary of are not as healthy as they seem.

These included vegetable crisps, margarine and salad dressing.

How should you eat breakfast?

As breakfast is the first meal of the day, what you eat in the morning could impact your hunger and craving levels for the rest of the day.

When we eat a carb, our bodies convert it into glucose and that goes into our blood. Our blood glucose levels then rise.

The quicker they rise, the quicker they fall - and that's what causes hunger, lethargy and sugar cravings.

Ian Marber, nutrition consultant and founder of The Food Doctor, previously told to The Sun: “A very high carb breakfast with little fibre and protein to slow the digestive process can lead to short-term energy as well as hunger, often within a couple of hours.

"As protein, fibre and fat all take far longer to break down in the digestive system, having a breakfast that includes these elements can lead to longer lasting energy.”

He suggested oats (carbs) with berries or chopped apple (fibre) and nuts (fat and protein).

Or, toast (carbs) with an egg (protein) and avocado (fat).