If you've ever eaten a ridiculously huge meal and ended up feeling full to the point of near-exploding, you might have entertained this negative thought: I've instantly gained weight.
Well, there's good news (and bad).
What you eat -- or overeat -- does not instantly turn into weight gain. How much you eat over the course of a few days or week, however, can result in weight gain.
To find out more about how long (and how much food) it takes to gain weight, The Huffington Post Australia spoke to two accredited practising dietitians.
"Weight gain simply happens when we have an imbalance between the kilojoules we're eating and the kilojoules we're burning off," Jemma O'Hanlon told HuffPost Australia. "It doesn't occur just from one meal -- it's when this imbalance occurs over a period of time that weight gain can creep up on us."
To put even more simply, Geraldine Georgeou says that "weight gain occurs when we don't burn off the calories we consume".
When it comes to getting the right balance, one meal can't ruin your weight loss efforts.
The key is to enjoy all foods in the right balance, keep your portions lean and focus on eating mindfully and intuitively.Jemma O'Hanlon
As with anything related to the body, the amount of food we need to eat before it ends up as body weight depends on the individual.
"The body is constantly working and using energy to complete tasks automatically without thinking, such as breathing," Georgeou told HuffPost Australia.
"The calories each person burns to keep our bodies going even at rest is known as our basal metabolic rate. Each person has their own energy requirement which varies depending on numerous factors such as age, height, illness and activity.
"What also varies is the rate at which people can burn their calories, otherwise known as your metabolism. We also use energy in order to complete conscious tasks such as walking, lifting and talking."
On top of this, the body then uses up energy when we exercise, meaning the more exercise you do the more energy you will burn off.
"When you stay the same weight, the energy your body gets from food equals the energy you burn off through automatic and conscious activity," Georgeou said. "Don't forget about incidental exercise. All the daily activities we complete like walking to the train station, taking the stairs or even doing household chores will add up."
But how much extra food equates to one kilogram of weight gain?
"If we're eating more kilojoules than our bodies are burning, the leftover energy will be stored as body fat," O'Hanlon said.
"One kilogram of fat is 37,000 kilojoules stored (as fat contains 37 kilojoules per gram, which equals 37,000 kilojoules per kilogram). To gain 0.5-1 kilogram per week, you'd need to be consuming roughly an extra 2000-4000 kilojoules each day."
In calories, this equates to an additional 500 plus calories per day that our body doesn't burn off, which isn't much at all.
"In food terms, that's roughly equivalent to two slices of pizza or two iced doughnuts," Georgeou said. "It doesn't take much to eat over your energy requirement."
Other foods that add up to around 2000 kilojoules/500 calories include:
- One Four 'N Twenty classic meat pie = 1680kJ
- One Big Mac from McDonald's = 2060kJ
- One Double Quarter Pounder from McDonald's = 3570kJ
- One large signature iced coffee from Gloria Jeans = 1720kJ
- One Zinger stacker burger from KFC = 3013kJ
- Large seasoned chips from KFC = 2070kJ
- One Banana coconut muffin from Muffin Break = 2340kJ
"Also to note, the average Australian adult consumes about 8,700 kilojoules a day, so some of these single items would be contributing to more than one-third of their daily intake," O'Hanlon said.
It's often when we eat past the point of being full that we're likely to gain weight.Jemma O'Hanlon
While the actual rate people can gain weight varies and depends on the individual and their metabolism, age, height, fitness and state of health, it does not happen overnight.
"When it comes to getting the right balance, one meal can't ruin your weight loss efforts," O'Hanlon told HuffPost Australia. "The key is to enjoy all foods in the right balance, keep your portions lean and focus on eating mindfully and intuitively.
"It's often when we eat past the point of being full that we're likely to gain weight. Eat slowly and listen to your body, and stop when you feel comfortably satisfied. If you're eating until you're stuffed full, chances are you're eating more than your body needs."
If you have weighed yourself at one time of the day and noticed your weight has increased a few hours later, O'Hanlon says this is not the result of 'instant weight gain'.
"We need to keep in mind that throughout the day our weight can fluctuate by a couple of kilos depending on our hydration levels or water retention, or whether we've just had a meal or something to drink," she explained.
This food or drink will first be digested, the waste excreted (to put it politely) and the excess energy stored as fat.
"As we start to digest our food our bodies will use this as energy," Georgeou said. "On average, it takes us roughly 6-8 hours after eating for food to travel through our stomach and small intestine. The food then travels through the large intestine where further digestion and absorption of water occurs, before it is then eliminated from the body.
"However, if we eat a meal with excess calories than we need -- our bodies will store this extra energy as fat to be used at a later time."
Frustratingly, it's much easier to gain weight than it is to lose weight.
"Often what we find, though, is that we can gain weight very quickly, while it takes much longer to lose it," O'Hanlon said. "Think about when you go on holidays. You may come back after a month or so away having gained five kilos, yet to lose that weight it might take quite a few months."
"When you consume extra food it can be extremely difficult to burn off," Georgeou said.
"For example, it would take a women in her thirties who is between 65-70 kilos 25 minutes of swimming laps to burn off a Mars Bar. A glass of wine would take approximately 40 minutes of brisk walking for your body to burn off and two chocolate biscuits at 80 calories each would take almost 20 minutes of jogging."
In saying all this (frankly horrifying) information, unless someone is overweight, obese or underweight, O'Hanlon says our weight is simply a number and shouldn't be focused on too much.
Our weight is just a number and it doesn't define who we are.
"The way our bodies are wired is extremely complex and there are so many different factors that affect our weight," O'Hanlon said.
"Rather than just focusing on our weight, we should be focusing on the bigger picture -- on our general health and wellbeing. Our weight is just a number and it doesn't define who we are."