Belly fat can affect even the slimmest of people, according to Dr Mosley.
The fat around your waist, or visceral fat, is “stubborn” but can be tackled if you eat the right foods and do the right exercise.
Dr Mosley has even stressed that reducing, or getting rid of, belly fat is “easier than you think”.
But first, the nutrition expert explained that to lose belly fat, “you have to understand belly fat”.
He continued: “And to understand belly fat, you need to understand the basics of how insulin works.
“Your body makes insulin after a meal in order to keep blood sugar stable. On your cell walls, insulin opens up glucose ports to allow sugar through – for burning in muscle, and for storage in fat.
“In your fat, insulin also curbs the release of fatty acids into your system. All well and good – as long as your insulin is working.
“However, as we age, cell-wall insulin receptors become less sensitive. As a result, even after a meal, our blood is replete with glucose and fatty acids.
“This is a toxic brew, driving an array of bad outcomes, including rapidly-expanding belly fat.”
However, Dr Mosley went on to explain that recent medical research has shown “you can lose belly fat, and you can lose it fast”.
The first step is to focus on your diet. The doctor said: “To make a serious impact on your belly fat, cutting out sugar-spikes is key.
“A surprising number of ‘diet’ snacks and drinks are high in sugar, and are marketed as diet foods because they happen to be low in fat.”
Dr Mosley recommended “limiting your intake of any food or drink containing more than five percent sugar to no more than twice a week”.
“This includes sweet fruits like mango and pineapple, and sugary smoothies and juices,” he said.
“Likewise, replace processed carbs like white bread, chips and pasta with slow-release energy sources, such as brown rice or quinoa.
“Two things will surprise you: the amount of sugar you were consuming unawares, and the speed at which your belly fat will begin to tame itself.”
Another method to consider if wanting to lose belly fat is intermittent fasting.
Dr Mosley said: “The idea that fasting ‘slows your metabolism’ is a myth. Under conditions of marked energy deficit – 800 calories per day or less – not only do you simply lose weight by eating fewer calories, but your body responds to the stress of fasting by enhancing hormone function to facilitate weight loss and burn fat for energy.
“Short-term fasting can lead to several changes in the body that make fat burning easier. This includes reduced insulin, increased growth hormone, enhanced epinephrine signalling and a small boost in metabolism.”
The doctor added: “According to a 2014 review of the scientific literature, intermittent fasting can cause weight loss of three to eight percent over three to 24 weeks.
“Not only this – but people lost four to seven percent of their waist circumference as well – indicating a large loss of the harmful belly fat in the abdominal cavity, strongly linked to chronic disease.
“So, you want to shift that weight round your middle? Try intermittent fasting.”