I wore a glucose tracker to monitor my holiday weight gain – here’s what happened

Glucose trackers, typically worn by people with diabetes, are increasingly being worn by people who aren't diabetic. Photo / Getty Images

What would one week of ice cream, souvlaki and wine do to my health in the long run? Here’s what a glucose tracker revealed.

If you’re anything like me, then the whole point of a week away on holiday is that you can eat and drink as much as you want, guilt-free. But how many of us can properly switch off? Too often, phantom calorie counts float next to the delicious treats listed on restaurant menus or presented in the windows of patisseries.

Inevitably, there is panic, as the jeans worn on the flight to somewhere sunny refuse to button on the return home. Add to this a long string of hangovers and the general sluggishness that follows a week of heavy dinners, and you can find yourself more drained by a trip away than you were before it.

Yet the positive effects that come with a week of R&R aren’t to be underestimated. Holidays can be good for the health of our muscles, hearts, brains and blood sugar alike. So, earlier this year, I went off to Greece armed with a glucose tracker and the determination to keep a food diary but still enjoy myself, to see how much damage a week of ice cream, souvlaki and wine can really do to your health.

The glucose tracker in my arm was there to tell me about how all of these carbs could “spike” my blood sugar, leading to potential consequences for my health later down the line.

Going to a Mediterranean country wasn’t cheating. Yes, there’s plenty of fresh vegetables and your food is more likely cooked in olive oil than butter, making it better for your heart and your skin. But there’s also deep fried feta, chips inside of massive pita wraps, huge trays of baklava, and many different kinds of spirits to contend with. I went to Athens and then an island, with two friends and my boyfriend, who, thanks to spending a lot of time in the gym, usually eats about 4000 calories a day. Foodwise I pretty much kept up with him for the whole trip away.

For breakfast on our first day I had a huge bowl of creamy full-fat Greek yoghurt, topped with tahini, banana, honey and nuts. Lunch was a halloumi souvlaki, stuffed with chips and some kind of delicious yellow sauce. I split a box of baklava as a snack with one of my friends and then for dinner, I had a huge bowl of orzo with mushrooms, a side of (more) chips, and dessert, a platter of Greek treats split between the four of us. In true first-night-away style we got through five litres of wine. In our defence, it was €11 ($21) a jug. (Then I went back to our AirBnB and ate four croissants meant for the morning to soak it up).

I might have earned some of that with a walk up the Acropolis (thankfully, we hadn’t planned it for the morning afterwards) but the rest of the holiday was spent lazing about. We all took it a bit easier on the booze but made up for it in food. Most mornings started with Greek yoghurt, but the nights ended with huge dinners, snacks afterwards, and a dessert like loukoumades (donuts covered in hard sugar) to finish. At home I try not to snack too much (a rule of keeping your blood sugar in check) but while I was away I ate anything I stumbled across that looked half-tasty.

All in all, I totally pigged out and I drank more than I do in an average month. What would this blip in my usual moderate lifestyle mean for my health in the long run?

How bad is it really to gain a few pounds on holiday?

I’m not here to tell you to starve on holiday. As personal trainer Dalton Wong helpfully puts it, “losing holiday weight is easy, but you’ll never get back the time that you spend away”. Yet the truth is that a sudden jump in weight can be jarring. When I got on the scale after my week in Greece, I weighed a full half a stone (3kg) more than I had done when I left. I’d be lying if I said it didn’t bother me.

Did all the cheese and pita bread I ate really do that much damage? Probably not, Wong says. “That jump won’t just be fat but also water retention, caused by eating a lot of salty food, and probably a bit of fat depending on how much you’ve eaten,” he explains. If you’re someone who does a lot of strength training, “you might even put on a bit of lean muscle mass, because you’re giving your muscles the good rest and nutrients that they need to actually grow”.

As Wong often reassures his clients, you would have to eat a truly enormous amount of food to put on half a stone of fat in a week. A single pound (45 grams) of fat gained requires “about 500 extra calories every day on top of the amount you need to maintain your weight,” he explains. As such, the reality is that a week of overindulgence likely won’t make you gain more than two or three pounds at most, even if, like me, you’ve ended up reaching to the back of your wardrobe for an extra pair of trousers.

I think I ate at least 4000 calories a day. To maintain my weight I need about 2000, roughly what I eat when I’m at home. It’s not all as simple as calories in, calories out, either, however. “Your body has a set point that it really wants to stay at,” says nutritionist Jenna Hope.

Once you return from holiday, your body works hard to bring your weight back down to its usual levels, a process that can be masked by water weight and constipation. “A week or two, or even three, outside of your norm might not actually cause weight gain at all, because you aren’t causing any long-term changes to your metabolic activity,” so long as you go back to your normal habits.

For this reason, Wong advises that you “avoid weighing yourself for four weeks after you get home,” he says. “Anything you see differently in the scales then might be actual fat, but until then, what you’re seeing likely isn’t real weight gain.” Sure enough, after a week back at home I was only 3 pounds (1.5kg) heavier than I was when I landed in Athens; after a month, I was back to my usual weight.

Given the power of your set point, shifting the weight can be as simple as “going for an extra walk after lunch,” says Wong. If you really are concerned about putting on weight on holiday, “either eat or drink your calories,” he advises. “Have the extra cocktail or the slice of cake, not both. You’ll likely be satisfied with one and feel a bit healthier afterwards.”

What happens on the inside?

The scales don’t tell the full story, however. Studies that examine what a week of overindulgence does to your body only present bad news. One Oxford University study reveals that three weeks of eating badly is enough to raise your risk of type 2 diabetes and cardiovascular diseases. Their participants were fed a diet high in sat-fats (crisps, cheese, chocolate and pizza) for 24 days, and while their weight didn’t budge, their cholesterol levels spiked by 10%, and the fat in their liver increased by a fifth.

A summer trip can also give you an “obese brain”, another recent paper from the University of Tubingen in Germany found (clearly, holiday-spoiling is a flourishing academic niche). Just five days of eating a poor diet is enough to cause changes to our brains that outlive “the timeframe of the consumption”, reports professor Stephanie Kullmann. After eating an extra 1000 calories a day for five days, “the brain and behaviour response resemble that of a person with obesity and changes in the brain seem to occur prior to weight gain”.

What can also change quickly is our gut microbiome. “A week or two weeks of eating differently and not getting enough fibre is long enough to see some changes in the makeup of your gut,” says Hope. The happiness of your gut is a core to good energy levels, proper digestion, immune function and even keeping you in a good mood. Spending time away in a totally different food environment is part of why we can come back from holiday feeling more sluggish and constipated than ever before.

From the food log before and after my holiday, and while I was away, it’s clear that I was eating more than I usually would for a few weeks on either side. I’d have an extra pint of beer or glass of wine on a Wednesday and I’d often veer towards something heavy in fat and salt and therefore attractive to my “obese brain” for dinner post-holiday. I’m sure that my gut was not impressed. “If you go away multiple times a year, it can be really hard to reset and not slide into bad habits,” Hope says.

Fortunately, this is easily avoided. “Preparing your breakfasts and lunches for the week that you’re back home can be really helpful, as it removes the element of spontaneous choice and helps you make better decisions,” says Hope. “It can be really helpful to order a grocery shop to arrive on the day that you’re back.”

To make it even easier for yourself, “try having a healthy breakfast on the days that you’re away, rather than diving into the hotel buffet and having everything you can see,” she adds. Having one healthy meal a day makes it much easier to get back to normal once you’re home, and if it’s high in protein, you won’t instantly reach for a snack as soon as you leave your hotel. (And if you’re in the land of thick, creamy Greek yoghurt, like I was, it won’t feel like a sacrifice.)

Will a holiday raise your blood sugar?

Blood sugar monitors are increasingly being worn by people who aren’t diabetic. The way they work is that you stick them into your arm (there’s a small needle, but you can’t feel it once it’s in), and then you can monitor the amount of sugar that’s in your blood after you’ve eaten from an app on your phone. Ups and downs are normal, but dramatic spikes after meals or prolonged periods of super-high blood sugar can indicate insulin resistance. This is a sign that your body is struggling to handle the amount of sugar you’re feeding it, and is a precursor for type 2 diabetes. Discovering the foods that “spike” you can help you prevent this in the long term, and this can also help you to avoid the sluggishness and fatigue caused by the crashes that follow.

It was interesting to see that a typical day in Greece eating a lot of carby and sugary foods made my blood sugar soar. But I can’t say it made me behave any differently. I did get a few weird looks from other tourists and it does ruin the bikini photos. The really useful bit came when I looked at my results after landing in Britain. I wore my patch, from Lingo by Abbott before, during, and after my holiday. In the week that I came home, my average blood sugar fell to being 95% lower than it had been while I was away.

At first I was shocked. Clearly my body had gone into panic mode because of how much I’d eaten. The stats sound dramatic on paper but in both cases, my average blood sugar remained in a “healthy” range overall, only briefly rising or falling to unhealthy levels. Such a return to normal is a good sign: “this shows that you’re in good metabolic health and that your body is responding with insulin in a normal way,” says Sophie Bertrand, Abbott’s nutritionist.

Your blood sugar levels are a result of homeostasis, the complex bodily process that keeps us functioning as normal. It’s hard to disrupt this process in a serious way by overeating for a week, Bertrand says. If you’re in your 20s and have a BMI that marks you as healthy, like me, then you can eat whatever you like for a short while and be fine in this regard, but this process works less well as you age. Seeing its effects was helpful. “Someone who’s older might find that they have more problems bringing their blood sugar down to normal,” says Bertrand. Over time, this is an issue that can raise your chances of developing insulin resistance, a major risk factor for type 2 diabetes. About 40% of us in Britain are insulin resistant.

With this in mind I’ll probably start approaching holidays a bit differently as I age. But regardless of your health, there are ways to get back to normal more quickly regardless of your age. Again, a protein-rich breakfast is king: “this will help to avoid big fluctuations in your blood sugar throughout the day,” says Bertrand. “Your sleep is also really important in keeping your blood sugar levels stable. Take the opportunity to grab a few more hours each night than you might at home.” Regardless of what you’re eating or how much you’re sleeping, a quick walk after dinner can work well “to balance out your blood sugar” too.

Besides, the chance to let loose can be good for us. Regularly going on holiday can lower your chances of dying from heart disease in the long run, and can also bring improvements to your blood sugar and “good” cholesterol levels. As Bertrand puts it, “a week of treats is much better than a routine filled with less healthy food or binges that follow restricting yourself too severely”.

Do you need to worry about your step count?

All of this ignores a fact that’s fundamental to the concept of holidays: a week or more of relaxation does us provable good. Stress – both the physical and mental kind – can wreak havoc on our health. If you’re the kind of person who exercises a lot, a week spent abstaining from lifting heavy weights or sprinting on the treadmill, presents a much-needed break for your joints and muscles. As a result, “some of the weight you put on while you’re on holiday might well be lean muscle mass,” says Wong.

That said, keeping your step count up can actually offset the potential damage done to your health by eating outside of the norm. “Going for a walk before or after dinner is a good way to help bring your blood sugar back down to a healthy range,” says Bertrand. And what’s more, you’ll probably find it easier to get them in while you’re away than you do at home. I certainly did: my average steps per day are 12,000 as per my health tracker, but I got in 15,000 a day in Athens, and it didn’t occur to me that I was exercising.

Do I regret letting loose on holiday? Not at all. As Jenna Hope says, the really crucial thing for your health is how quickly you go back to normal after your holidays, and making sure that you don’t live with your “holiday brain” between them. Next time I go away, I’ll be sure to plan some healthy meals for the week that I get back, and I’ll try to find ways to keep my step count up while I’m away too, to counter the effects of eating badly. I’m not sure that I’d take a glucose tracker with me again, but it’s certainly helpful to know that beer spikes me more than wine, and that baklava does less damage than chips. Best of all is that, having looked at the changes to my body, I now know that with some thought, I can keep enjoying holidays the way I want for the rest of my life.

Lauren’s diet: At home v abroad

At work

• Breakfast: Greek yoghurt (low fat) with raspberries and chia seeds
• Lunch: Tofu or eggs with some veg and rice
• Dinner: A bowl of pasta, a stir fry or vegetarian chilli
• Snacks: Some fruit or a protein bar
• Alcohol: I try to keep drinking for the weekend. I’ll have a couple of glasses of wine or a few pints of beer most Fridays and Saturdays
• Exercise: A 30 minute run in the morning or a yoga or pilates class in the evening. I usually manage 10,000 steps a day and I also do strength training twice a week

On holiday

• Breakfast: A big bowl of full fat Greek yoghurt with lots of peanut butter, some fruit, and honey
• Lunch: Souvlaki with chips
• Dinner: A big shared meal out with different vegetables (usually deep fried) and cheeses, and a main like orzo
• Snacks: Ice cream, baklava, spanakopita, (more) cheese, loukoumades
• Alcohol: As much as I wanted – mostly beers and wine but also cocktails and tsipourou (I can’t stand ouzo)
• Exercise: A few long walks and plenty of roaming about in Athens