It's a frightening, much bandied about statistic that I am determined not to reinforce.
I overhear it as I stand on a blindingly blue-sky morning on Auckland's waterfront, admiring the towering, floating hotel that is going to be my home for a fortnight.
It surfaces again in the fast-moving queue of passengers being offered lollies and drinks as we board the Celebrity Solstice superliner.
And a smiling retired woman from Atlanta issues her kind warning as my eyes widen on entering the sprawling Oceanview Cafe buffet - my second stop after a brief look-in to my surprisingly spacious balcony room.
"You gain a pound a day on cruises, you know," the trim, well-groomed veteran of more than 15 cruises tells me as I marvel at spotless stations offering everything from salads to soups, roast to fish, burgers to pasta, appetisers to dessert, Mexican to Indian food.
I can well believe her. With 10 dining venues offering top-class food at every time and turn, and room service included in the fare too, I know this trip will be the most pleasant of battles against my genetically ingrained love of food. But a pound a day? On a 14-day cruise that would come to more than 6kg!
There's a lot I will put up with for my craft. I will brave potential sea-sickness - which mercifully doesn't arise - as I sail in luxury to the Bay of Islands; Tauranga; Wellington; Akaroa; Dunedin; Dusky, Doubtful and Milford sounds; Hobart; Melbourne and Sydney.
I will sample the spas, swimming pools and beauty treatments. I will watch all manner of entertainment - from revues to comedians, musicians to magicians - and attend talks, trivia, ballroom dancing and bingo.
I will sample wines of the world (there are 420 on offer) and spiced and scented molecular cocktails. I will have breakfast on my balcony, and dinner as I watch a blockbuster on my big-screen TV.
I'll even eat five multi-course meals a day to make sure you, the reader, get the lowdown on holidaying on the high seas. But put on 6kg? There I draw the line.
There's only one thing to do.
So, after a delicious self-selected sampler lunch of beef tortillas, vege dumplings, paella, poached fish, couscous and green salad, I swear off elevators for the rest of the trip - not a small commitment on a 16-deck ship that's almost a third of a kilometre long - and go hunting for the gym.
My mission takes me past the outdoor swimming pool, where people already bask in prime poolside spots, or read or sleep in the shade. Through the tranquil indoor Solarium pool, a child-free zone for all but family hour in the late afternoon, I go. Past reception to the AquaSpa with its trove of treatments, I find what I'm looking for.
The fitness centre teems with people of all ages familiarising themselves with the strength and cardio equipment, booking for Body Sculpt Boot Camp or personal training, signing up for enticingly titled seminars (Eat More to Weigh Less, Secrets to a Flatter Stomach), or just working out - already.
Trainer Jake Shally, 21, from Noosa, tells me quite a few people use a cruise as an opportunity to try to get fit, or kickstart a return to health. He also says the quietest time at the fitness centre is 6pm - when everyone is heading to dinner - or on the days we're docked.
Not being a regular gym attendee - somehow a full-time job, three kids, a husband and sleep seem to take up all my time - I'm excited and intimidated by all the options.
Being both unfit and unco-ordinated, I hesitate to commit to boot camp or paid pilates, yoga or tour de cycle classes.
Complimentary morning stretch and Fab Abs classes will do me nicely. I'll try the treadmill or outdoor jogging track daily, and participate in the Zumba and intriguingly titled "Insane Workout with Ships Officers" when they're offered.
The exhausting task of planning my fitness schedule sorted, and a bit of unpacking and minor exploring aside, I find myself gravitating back to the buffet for an "afternoon tea" of sushi, cheese and crackers, and a nibble of two desserts. Too soon after, it's time for sail-away snacks with the other members of my party.
Red and black caviar, spice-encrusted goat's cheese balls, deep-fried prawns, mini-lamingtons and fruity pastries...
Perhaps I'll need that boot camp after all, because straight from here we're off to dinner at the Grand Epernay Dining Room.
A double-storey glass wine tower is the impressive focus of the 1429-seat restaurant that is the hub of dining on the Celebrity Solstice. A huge chandelier effervesces with glass bubbles above. The linen is a pristine white, the service of head waiter Marko from Croatia, assistant waiter Kolka from India and sommelier Eric from the Philippines is exemplary. On the days to come they will remember all my culinary quirks and preferences, even when I'm dining at one of the other nine venues - no mean feat considering there are about 3000 guests on this cruise.
At this stage my story could easily degenerate into an endless list of varied and outstanding dishes from the Grand Epernay (which is included in the fare) and the speciality restaurants that offer additional choices for a modest surcharge.
Steak Tartare with Dijon mustard, parmesan, vinaigrette and crispy potato chips from the Tuscan Grille Italian restaurant.
Hunan beef with peppers, oyster mushrooms, bamboo shoots and red Thai chillies at Silk Harvest Asian fusion restaurant. Lobster with smoked bacon and Dijon cream, cognac-flambeed at our table at Murano, a restaurant so sophisticated that I am offered a black napkin rather than a white one to go with my black dress.
The Epernay's seared tuna is tender and succulent, and the rare kangaroo steak so good that I am more grateful than embarrassed when Marko brings another helping "for the table".
But I'll try to contain myself. After all, Celebrity Solstice is a high-class hotel - which happens to be cruising from beautiful place to beautiful place - and the food should therefore be nothing other than excellent. Still, it's difficult not to marvel at such high standards when you take into account the scale of the operation.
There are 160 chefs and cooks employed to make more than 15,000 meals a day for the 4250 passengers and crew. There are nine galleys and 23 preparation areas to make these meals, as well as to cater for those with vegan, vegetarian, kosher and other dietary requirements.
Every dish, every type of bread you can't resist, every dessert you drool over, every icecream you indulge in is made fresh every day and as close to service as possible. At Grand Epernay, each steak and piece of fish is grilled to order.
Overseeing this impressive food operation is 45-year-old executive chef Geoff Haviland. Celebrity Solstice is the Australian's first sea posting in his 26 years in the hospitality industry, 15 of those as executive chef of top hotels in Dubai, Hong Kong, Germany, London and most recently Palazzo Versace on the Gold Coast.
He's the one we see at the Oceanview Cafe doing quality checks during service. He's in charge of keeping food waste and spoilage down to 8 per cent - which gets turned into slurry onboard and is discarded as "healthy fish food" at least 12 nautical miles off shore.
He's the one who decides how to spend the US$1.5 million (NZ$1.8m) on food per 12-day cruise. He orders the dry goods and frozen food, seafood and meat three months ahead of a cruise; and he plans the perishables bought locally - the fruit, vegies and herbs, the top-ups for meat, the barramundi, crocodile and kangaroo.
The last three ingredients are an example of yet another one of Chef Geoff's duties - to cater for different nationalities according to the location and manifest of the cruise. With Celebrity Cruises being an American company, it's no surprise that at least half the guests on our cruise are American, but the other half are Australian, with a smattering of Kiwis, Canadian and Brits, and that means some interesting changes to the menu.
Apart from region-specific items such as crocodile or pavlova, Haviland needs to make other allowances. Aussies tend to drink 10 times more coffee and eat far more seafood and vegies (which they like crisper) than Americans. Kiwis, Aussies and Brits like whole pieces of grilled bacon; Americans like their streaky bacon crispy. Antipodeans prefer a more casual style of dining, the British like it more formal. And if there are more children on board (our cruise has only about 200), he needs to have more burgers and fries - not just for the kids, but also for the parents who end up eating them in addition to everything else.
Haviland does galley tours, oversees the popular on-board food presentations - hundreds attend one at the 1200-seater Solstice Theatre on how to cook the perfect steak - and he still cooks on the line every night.
But the food-safety of guests is the top priority of the indefatigable chef and his team. The stainless-steel galleys are cleaned daily from floor to ceiling. He inspects them rigorously.
Stewards dispense hand sanitisers at the entrance to each dining area, serving tongs are changed every 20 minutes, and for the cruise's first 72 hours - the incubation period of the norovirus - staff serve all guests at what will become the self-service buffet. When one of our party falls ill with suspected gastro, she is voluntarily confined to her room for 24 hours, with her key card disabled and a limited menu served in her room on disposable plates, with disposable utensils, by a gloved attendant.
By day five, I wish someone would confine me to my room and make me eat a limited menu.
Yes, I've been going to the gym every day, sometimes twice. But I've also valiantly eaten my way through most breakfast options - cereals, muesli, fruit salad, yoghurt, omlettes, muffins, waffles, pancakes, bacon, eggs any way you can think of - although I did draw the line at kippers. I've tried the more formal set-up of having breakfast and lunch at the Grand Epernay on sea days and found the Oceanview buffet style of dining more to my taste - although harder on my waist. I've sampled four or five courses every night. Enough is enough.
So, day five is the day I stop eating as if each meal is my last and abandon my Hobbit-inspired Elevensies... and Threesies (a three-course snack formerly known as afternoon tea)... and Five-thirties (that's the time the sushi gets rolled out).
From here on in, I cut down portions and courses and try to choose the healthier food options. And there are plenty of them, not only a vast selection of fruit and vegies, but also menu items with wholegrains, or lower salt and sugar content. I couldn't eat this healthily at home if I tried .
Finally, I start to enjoy the journey as much as the degustation.
But what about that frightening statistic I was hoping to avoid reinforcing? Well, the extra pounds I bring home from this unforgettable cruise are, happily, only in the form of presents rather than curves.
The writer was a guest of Celebrity Cruises.
- Sunday Star Times