You've just started a new workout routine and eating a more healthy diet (after noticing those jeans have in fact not shrunk, *sigh*), and you're asking this one important question: How long does it take to lose weight?
Is it a few days? Please, be yes. A few weeks? A few months?
"Physiologically speaking, to lose weight you must burn more calories (through physical activity) than you eat or drink," Clark told HuffPost Australia.
"Basic body functions (breathing, nerve function, manufacturing cells, blood circulation and maintaining body temperature) use 50-70 percent of your calories or energy. The rate at which your body uses calories/energy for basic body functions at rest is called the basal metabolic rate (BMR)."
Additional factors that strongly determine your BMR include your genes, age, gender and body composition.
"Therefore, much of your energy use is predetermined," Clark explained. "However, the amount of energy you burn each day also depends on how much exercise you do (intensity, type and duration)."
Once we consume more than our bodies need over a period of time, this then turns into weight gain.
How long it takes to lose weight
While this depends on the individual as every person's body and goals are different to one another, if you begin to exercise three times a week and eat a healthy diet, you may find you lose weight quickly.
"There is no calculation for this as every individual is different and how their body responds to exercise will differ, as well," Clark said.
If an individual is significantly overweight and has more weight to lose than the average person who wants to lose five kilograms, they might lose more weight more quickly, Clark explained. However, this weight loss may be a combination of fluid loss and fat loss.
"For someone who has started exercising three times a week and eating a healthier diet, they may expect to lose one kilogram in 1½-2 weeks," he said. "This is also dependant on the type of exercise they are performing and the duration and intensity of their training."
McDonald agrees, explaining that your 'training age' has a lot to do with how much weight you can lose.
"[Weight loss] really depends on where you are starting at in terms of your base level of physique. By that I mean what is your training age, which is the number of years you have trained for," McDonald told HuffPost Australia.
"An example might be if you had not trained in years and put on 20 kilograms of weight, in particular around the midsection. Once you got into a routine of training, say four times per week and living by the 80/20 rule with your nutrition (80 percent good food and 20 percent bad), no doubt you would see a noticeable shift by the end of the first fortnight by potentially a few kilograms."
For someone who is new to training and doing 3-4 sessions per week while eating correctly, you can expect to lose anywhere between 0.5-2kg per week, depending on just how much weight they need to lose.
However, if you had been already training three times per week and eating well, and decided to ramp it up to 5-6 exercise sessions per week and refine your food, then you may find a much smaller amount of results.
"There is no magic formula when it comes to predicting weight or fat loss," McDonald said. "In saying that, from experience, for someone who is new to training and doing 3-4 sessions per week while eating correctly, you can expect to lose anywhere between 0.5-2 kilograms per week, depending on just how much weight they need to lose.
"The main things to remember are that, if you are serious about results, you want to train four times per week ideally and follow the 80/20 rule above. This alone should make a different to your body composition and overall health."
Why it's harder to lose weight than to gain it
As we all know, it's much easier to gain weight than it is to lose it. While this is primarily due to habit (if we're used to eating cake every day, it's ridiculously hard to stop), according to Clark and McDonald, there are a few other reasons why it can be difficult to shift weight.
"I think it's important to note that the biology of weight loss and weight maintenance is a complex process," Clark explained. "There are so many factors that contribute to overweight and obesity such as diet, inactivity, genetics, smoking, motivation, alcohol consumption, stress, poor sleep hygiene, occupation, environment and hormone imbalance, to name a few."
Underlying health issues
"If you are struggling to lose weight, it's important to rule out any underlying causes first and foremost," Clark said. "There could be a medical reason for your struggle such as a chronic health condition like cardiovascular disease or type 2 diabetes, or a hormone imbalance such as your thyroid, sex hormones, insulin or cortisol."
"In today's world I believe the biggest factor that influences weight gain is stress, both physiological and psychological," McDonald told HuffPost Australia.
"When your stress hormones such as cortisol are elevated in your body for prolonged periods of time it limits your body's ability to burn body fat, so when you factor in work stress, family stress, training stress, financial stress and so on, people end up being in an overly stressed and exhausted state.
"Over time this can lead to a large build up of visceral fat, which can be hard to shake."
Dieting and ageing
Although dieting can be a tempting method of quickly losing weight, Clark said the negative effects of dieting far outweigh the positive.
"Other factors that contribute to difficulties losing weight include regular yo-yo dieting, mindless eating, sedentary lifestyle and slowing metabolism that comes with age," Clark said.
"These factors predominately influence your hormone function, which plays a major role in your body's ability to lose weight.
"For example, weight cycling or yo-yo dieting can change your physiology. A reason for this is that through constant dieting your hunger hormone (ghrelin) increases and your fullness hormone (leptin) decreases. As a result, you will feel hungrier and less satiated every time you eat."
How to lose weight in a healthy, sustainable way
In order to lose weight safely and in a way that you will actually be able to follow for more than a week, Clark and McDonald recommend the following.
1. Be realistic with your weight loss goals
"A guide to follow for safe and sustainable weight loss is to aim for 0.5–1 kilogram per week. In order to lose one kilogram per week, you would need to burn and reduce your dietary intake by approximately 1,000 calories per day," Clark said.
If you're thinking 1,000 calories per day is completely unachievable, it equates to a one hour HIIT session (around 800 calories) and eating one less snack (around 200 calories).
"Having said this, it is also important that you create as much food variety as possible so you don't put yourself at risk of malnutrition or nutrient deficiencies."
2. Avoid dieting and skipping meals
Not only is skipping meals bad for your mood, energy levels and overall health, but it can also affect the way you eat later on.
"If you do skip meals, you are more likely to eat more when you do eat, and this may lead to a larger stomach capacity," Clark said.
"Crash dieting is a short term solution that will increase your body fat levels in the long term due to your body lowering its metabolic rate as a result."
3. Exercise regularly
"Train four times per week for 45-60 minutes per workout," McDonald said. "While three times per week is good, four times per week is much better."
For best results, Clark recommends doing a combination of resistance (weight) training and cardiovascular training.
"Think of strength training as the main course at a restaurant -- cardio and yoga are all the equivalent of an entrée. So strength training is the foundation of health and fitness," McDonald added.
"To stay in shape you need to teach your body to be healthy -- by being consistent with your training and nutrition week in and week out."
4. Cut down on the refined carbs
"Refined carbohydrates such as cake, biscuits, cookies, muffins, chips, cupcakes, soft drink, fruit juice and most supermarket breads will make you store fat if not burned off," Clark explained.
5. Watch your portions
"Be cautious of portion size of main meals and snacks -- always eat to 80 percent full before returning for seconds," Clark said.
6. Avoid drinking your calories
"Don't drink your calories -- avoid beverages that contain 'empty' calories and don't fill you up such as soft drinks, large fruit juices and energy drinks," Clark said.
7. It's never too late to start (or to try again)
"Health is in the mind, so remember you are never too late to start and it is never too late to rekindle your passion for health and fitness," McDonald said.