What Sugar is Doing to Your Body

(CNN) It's 7 a.m., your train is late, you're exhausted and stressed, with another long day at work ahead of you.

It's the kind of moment when many of us reach for a hot drink.

But these daily pick-me-ups might come at a much higher price than the $4 you pay at the till.

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A drink you buy at Starbucks could contain up to 25 teaspoons of sugar per serving, according to a new report by British campaign group Action on Sugar.

That's three times the amount of sugar in one can of Coke, and more than three times the maximum adult daily intake recommended by the American Heart Association. In a response to the report, Starbucks says it has committed to reduce sugar in its "indulgent drinks" by 25% by the end of 2020.

The research focused on drinks sold in the UK, but nutritional information published on the companies website show that sugar levels are similar in the U.S. and elsewhere.

To find out what sugary hot drinks are doing to our bodies, CNN spoke to endocrinologist and obesity expert Dr. Tony Goldstone from Imperial College London. We asked him to lay out the health risks in the short, medium and long term.

Your body an hour later

Right about now, you may be having a sugar crash. You might be feeling "a bit sweaty, a bit sick, and disorientated," says Goldstone. You may even have a rapid pulse.

When you are consuming sugar in hot drinks, it's easy to drink a large volume of liquid in a short time, and any sugar it contains is very rapidly absorbed into the body. It would, for example, be much harder to consume the same amount of sugar if it was in the form of rice. It's one of the particular problems with sugary hot drinks, says Goldstone.

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So you have a spike in sugar levels in the blood -- and as everyone knows, what goes up must come down. The pancreas releases lots of insulin in response.

A very high rise and rapid fall of sugar in the bloodstream may be bad for health -- it may put you at risk, says Goldstone, of laying down of fat under the skin and, more worryingly, in the guts, liver and pancreas (more on that later).

By now, you probably want to have something else to eat as the crash stimulates your craving for food.

After a year of having a sugary hot drink every day

If you've been drinking sugary drinks like these regularly, you might, says Goldstone, be in the beginning stages of insulin resistance -- and at higher risk of diabetes in the future.

Your body can only deal with so many excess calories -- the rest gets stored as fat. Some fat can be stored under the skin, but more worryingly, the body can also lay it down around the guts and in the liver and pancreas.

"Fat is a very active organ, it releases lots of chemicals and hormones that are damaging to health and cause inflammation," Goldstone says.

Fatty deposits can impair the way the liver works -- while the pancreas can be stressed by constantly over-producing insulin to cope with all the sugar.

Your body after 10 years

After a decade of one drink like this a day you may have put on 10 kilos (22 lbs), and if you're middle aged then you are significantly increasing your risk of diabetes, says Goldstone.

"Obviously there are a lot of genetic predispositions," Goldstone adds.

What's unnerving is that you can store a lot of fat around your organs without necessarily looking overweight.

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Goldstone has scanned the livers and abdomens of middle-aged men who sit in their offices a lot and says he "can be quite shocked" at what shows up.

"Inactivity, alcohol, sugar, genetics" can all affect the way the body stores fat, says Goldstone, adding that, "You don't necessarily know it -- just like you can have high blood pressure and not know it -- you can have fat in the your liver and abdomen and not know it."

He says that exercise is key: "You may not lose much weight when you exercise, but you may have more muscle and less fat. Exercise helps get rid of fat in the liver and tummy -- fat in the liver is very sensitive to exercise. Fit and fat is better than not fat and unfit."