If you think the cereal you pile into your bowl is good for you, think again.
Researchers found Kellogg's Frosties to be the worst offender in the UK, containing 11.1g of sugar per 30g serving - the equivalent of almost three teaspoons of sugar.
In a larger 100g serving (we're talking a large bowl full of cereal), there are 37g of sugar - that's more than nine teaspoons of sugar.
Coco Pops and Crunchy Nut Cornflakes were the second most sugary, with 11g per 30g serving, followed by Nestle's Lion cereal, which contains 8.7g (more than two teaspoons of sugar) per small serving (30g).
To conduct the research, experts from the UK-based World Action on Salt and Health (WASH) selected 19 products manufactured by Kellogg and Nestle/General Mills, from 29 countries.
Over half of the cereals analysed (58%) were found to have high levels of sugar, with 55% of the cereals surveyed containing half the daily recommended intake of free sugars of a three year old in one serving.
It's also worth noting that while most cereal packets show the sugar content per 30g serving, most of us will eat nearer 60-100g (a bowl full).
The cereals containing the most sugar were:
:: Kellogg Frosties - 11.1g per 30g serving / 37g per 100g serving
:: Kellogg Coco Pops - 11g per 30g serving / 35g per 100g serving
:: Kellogg Crunchy Nut Cornflakes - 11g per 30g serving / 35g per 100g serving
:: Nestle Lion cereal - 8.7g per 30g serving / 29g per 100g serving
:: Nestle Nesquik - 7.5g per serving / 25g per 100g serving
:: Nestle Cookie Crisp - 7.5g per serving / 25g per 100g serving
:: Nestle Cheerios Honey - 7.2g per serving / 24g per 100g serving
:: Kellogg Frozen cereal - 6.3g per serving / 21g per 100g serving
:: Nestle Cheerios Multigrain - 6.3g per serving / 21g per 100g serving
:: Kellogg Special K - 4.5g per serving / 15g per 100g serving
:: Kellogg All Bran Flakes - 4.2g per serving / 14g per 100g serving
:: Kellogg Rice Krispies - 3g per serving / 10g per 100g serving
:: Kellogg Corn Flakes - 2.4g per serving / 8g per 100g serving
The report also found huge disparities in the levels of salt and sugar found in the same branded breakfast cereals sold in different countries.
For example, a 30g serving of Frosties in Australia contains 12.4g of sugar, while in Ireland the same amount contains 11g of sugar.
Graham MacGregor, Professor of cardiovascular medicine at Queen Mary University of London and Chairman of WASH, said: "It is shocking that breakfast cereals still contain extremely high levels of salt and sugar.
"Kellogg and Nestle are the two main global manufacturers of breakfast cereal and they need to demonstrate that they can act in their customers' interest to reduce sugar and salt levels to help save lives."
In response to the report, a spokesperson for Nestle told The Huffington Post UK: "We're committed to providing our consumers with a nutritious start to the day and have made significant progress in reducing the sugar and salt content of our cereals over the past decade without compromising on quality or taste.
"Across countries, we've reduced the sugar in our products by up to 30% and offer low or no added sugar cereals such as Shredded Wheat. Globally, we have also removed over 7,000 tonnes of salt.
"Cereal is a convenient and nutritious breakfast choice with our products containing more of the good stuff – grain, vitamins and minerals – than either sugar or salt."
A Kellogg spokesperson said: "For more than a decade, Kellogg has been committed to reducing the sugar and sodium in our cereals while providing positive nutrition and great taste.
"There may be variations in recipes around the world due to consumer preference, but we are proud of the progress we've made against our global sugar and sodium reduction targets we set to achieve by 2020.
"The majority of our cereals now have 10g (about 2.5 teaspoons) or less of sugar per 30g serving, and by 2020, 90% of our Kellogg's cereals will have 10g of sugar or less per 30g serving.
"In the UK alone, we will have removed more than 2,000 tonnes of sugar in our cereals by the end of next year.
"In addition, in 2015 we exceeded our global goal of a 30 percent overall sodium reduction in ready-to-eat cereals five years ahead of schedule. And by 2020, at least 85 percent of our cereals will have 150mg or less of sodium per 30g serving."
For those who are worried about getting a healthy start to the day, nutritionist Charlotte Stirling-Reed recommends trying 'overnight oats', a low sugar, wholegrain cereal or wholegrain toast.
"It takes less time than it takes to boil a kettle to put together the night before," she explained. "It then soaks in the fridge over night and is ready to consume first thing in the morning."
She added: "Low sugar, wholegrain breakfast cereals are also a good idea and a quick fix – I'd always recommend adding some of your own fruit to increase the flavour profile and nutrient content too.
"For me I also love peanut butter on wholegrain toast as a fairly quick and nutritious breakfast which also gives me plenty of energy to get me through most of the morning too."