Live Science Plus
How long does it take to lose weight?
Weight loss can be frustrating when you want to see results quickly — so how long does it take to lose weight? And is there any way to speed up the process?
How long does it take to lose weight? In the age of instant gratification and dubious marketing claims, it may be difficult to have realistic expectations. Not to mention that when you feel uncomfortable in your own skin, and your health seems to be getting worse, you may be tempted to set yourself an ambitious weight loss goal.
This is understandable. A big target number may make you feel more motivated and eager to start your transformation. But excessive weight loss can not only lead to the dreaded ‘yo-yo effect’ (where you lose weight, only to put it back on), it can also be unhealthy. What’s more, some people will find it way more difficult to shed unwanted pounds than others. So what is a realistic weight loss rate? And what factors can affect it?
Before we dive into the science of weight loss, it is important to point out that there is no real ‘ideal weight’ to aim for. Medical professionals often rely on a person’s BMI to determine what is deemed to be a ‘normal’ weight range. But this measurement is not without its flaws.
The number on the scale will not tell you how much muscle mass, as opposed to fat mass, your body contains. It won’t indicate whether you struggle with water retention, either. It’s therefore important to take an individual approach before setting a weight loss target. And the first step is always to consult a dietician or medical professional for professional advice before embarking on a weight loss program.
How does weight loss occur?
Your calorie expenditure – that is, the exact number of calories you burn each day – is composed of three major components.
The first is referred to as Resting Metabolic Rate (RMR). It consists of the Basal Metabolic Rate (BMR) – the minimum number of calories your body needs to maintain normal bodily functions, such as breathing and pumping blood – as well as low-effort daily activities, such as eating, walking for short periods (for example, to use the bathroom), sweating or shivering.
The second component is referred to as the Thermic Effect of Food (TEF) – the additional energy needed to digest, absorb, and use the nutrients you consume. According to the Journal of the American College of Nutrition, TEF is increased by larger meal sizes, intake of carbohydrate and protein, as well as low-fat plant-based diets.
Get the world’s most fascinating discoveries delivered straight to your inbox.
The third component is referred to as the Thermic Effect of Activity (TEA) – the number of calories burned during exercise. TEA can also include Non-Exercise Activity Thermogenesis (NEAT) which is the amount of energy expended during light activities such as fidgeting, cooking and shopping.
In order to lose weight, you have to maintain a consistent calorie deficit. When you burn more calories than you consume, your body will dip into the energy reserves stored in your fat tissue. Conversely, when you eat more calories than your body needs, you will start gaining weight.
Now, all food and drink will add to your daily calorie tally, and it’s interesting to learn how calories are calculated given this is how you’ll be keeping track of your energy intake. At the same time it’s also worth noting a couple of myths surrounding energy expenditure and weight loss.
Many believe that eating smaller, more frequent meals can improve your chances of shedding unwanted pounds, for example. But while it is true that some will find this approach helpful for appetite regulation, as scientists from the Nutrition Reviews journal point out, there is not enough evidence to claim that meal frequency is linked to calorie burning.
Another misconception is that deep intellectual work can increase your energy expenditure. Unfortunately, thinking doesn’t burn calories.
What factors affect weight loss?
Age
As we get older, our body composition changes. We lose muscle mass and gain more fat. Regular physical activity and a healthy diet can delay this process, and many elderly adults boast great muscle strength and endurance. However, this is not the only implication of the aging process.
As described in the Nutrition journal, there is evidence to suggest that the metabolic rates of our internal organs become progressively lower in older people. These organs also become smaller. As a result, they need fewer calories to function properly and this will have a significant impact on our overall energy requirements.
Sex
In general, men will find it easier to shed unwanted pounds, but our biological differences are not as straightforward as this. As stated in the Medicine & Science in Sports & Exercise journal, men have a Resting Metabolic Rate that’s between 5% and 10% higher than women of a similar frame. This is because women tend to carry more fat than muscle, and fat tissue is less metabolically active.
But this does not automatically mean that women will lose less weight when put on the same diet as men. According to a systematic review published in the Obesity Reviews journal, the effect of weight loss interventions are not significantly different between the two sexes, and there is little evidence they should adopt different weight loss strategies. It could be that other factors, not only the body composition, may be at play.
Activity level
The more physical activity you carry out, the more calories you are able to burn. But time spent working out is not the key factor here – intensity is important.
Going for a leisurely walk or attending a gentle yoga class will not have the same effect as running for 10 kilometers. How you exercise and how you progress with your physical activity is equally important to your activity levels.
According to a review published in the Obesity Reviews journal, adding more resistance training to your routine will help you to retain and build more muscle mass. Muscle is a very metabolically active tissue, so more muscle means a higher RMR, and more calories burned at rest.
Some fitness professionals debate whether High Intensity Interval Training (HIIT) is superior to steady-state cardio (such as cycling or jogging) in terms of the number of calories burned. But as described in the Obesity Reviews journal, they both show similar effects on body composition – scientists point out that HIIT may be more time-efficient as it requires nearly 40% less training time.
Hydration level
Does drinking water help you lose weight? Hydration definitely plays a role in weight loss, although its effect is not direct. According to the Frontiers in Nutrition journal, drinking more water helps to reduce portion control and increase lipolysis – the breakdown of fat tissue.
Animal studies also demonstrated that dehydration can lead to hormonal changes that may increase the risk of obesity and associated diseases. Wondering how much water you need to drink? The recommended intake is 2L a day, but the exact amount your body needs will depend on several different factors.
Genetics
Your genes may be partly to blame for why you struggle to lose weight. As reported in the Genes & Nutrition journal, a growing number of studies identify gene variants that are associated with an increase in fat mass. These variants may interact with specific environmental factors and increase the risk of obesity.
Sleep
Does sleeping burn calories? Not exactly. But maintaining good sleep hygiene can make all the difference to your weight loss efforts. Research in the Nutrients journal found that just one sleepless night has been shown to increase your desire for high-calorie, nutrient-poor foods, such as cookies and sugary beverages. Disturbed sleeping patterns tend to lead to increased calorie consumption too.
It will also wreak havoc on the levels of hormones associated with appetite control. A study published in the Sleep journal suggests that just an hour less sleep five nights a week may lead to a lower proportion of fat mass loss in individuals on low-calorie diets, despite similar weight loss. What’s more, ‘catch-up’ sleep may not completely reverse these far-reaching changes in body composition.
Stress
Psychological stress is another factor that may impact the rate of your weight loss. The Obesity Reviews journal found that feeling under pressure may lower the quality of your sleep, enhance your appetite, intensify your cravings and decrease your motivation to exercise.
At the same time, there is growing evidence that the practice of mindful eating can reduce food cravings and increase your chance of achieving your weight loss goals.
Gut health
Can you take probiotics to lose weight? It may be effective. Scientists are increasingly pointing to gut health as a factor in obesity. According to a review published in the Gastroenterology journal, the amount and the type of gut microbes residing in our intestines may dictate the rate of your weight loss.
For example, bacterial strains like Ruminococcus gnavus were found to be more common among obese individuals. Their presence also decreased during weight loss. Meanwhile, the number of bacterial strains such as Akkermansia muciniphila and Alistipes obesi were higher in lean individuals.
Hormones
Certain hormonal disorders will have an impact on the rate of your weight loss. Hypothyroidism is a good example – a condition in which the thyroid gland does not produce enough metabolism-boosting hormones, which in turn can promote weight gain. As reported in the International Journal of Obesity, higher baseline levels of thyroid hormones were linked to better weight loss outcomes.
How much weight should you lose per week?
How long does it take to lose weight in a healthy and sustainable manner? According to the Centers for Disease Control and Prevention, people should aim for a fairly steady weight loss rate of about one to two pounds a week because this way they are more likely to keep the weight off in the long term.
Yet scientists are questioning this claim. A study published in The Lancet journal demonstrated that the rate of weight loss does not seem to affect the proportion of weight regained within 144 weeks.
Another study, published in the Obesity journal, found that, in people with a similar total weight loss, the rate at which they lost weight did not affect how many pounds were later piled back on. Nonetheless, those who were prescribed a diet with the least number of calories lost the most muscle mass.
Still, dieticians recommend taking a gradual approach, as it promotes healthier attitudes to food and it is least likely to cause side effects.
“If you want to maintain the results in the future, it is recommended to focus on a slow but healthy weight loss where you lose one to 2 lbs per week, says Wendy Lord, registered dietician at HealthReporter. “Although such a journey is slow, its constancy will make it easier to develop healthy eating habits, making it less likely that you will gain weight again, and most importantly, it is much safer than rapid weight loss.”
But what about overall weight loss? “When healthily losing weight, you can expect to lose up to 8 lbs in a month and even up to 90 in a year. However, it is worth remembering that such impressive numbers will only be realistic if you lose up to 2 lbs per week for the whole year and if you are obese in the first place,” says Lord.
Can you speed up weight loss?
What is a dietician's stance on boosting metabolism?
“Speeding up weight loss is definitely possible, but it won't necessarily be healthy,” advises Lord. “Since losing weight too fast can lead to loss of muscle mass, slowed metabolism, lack of nutrients in the body, and many other problems, it is recommended to consult a specialist.
“On the other hand, there are certainly a few lifestyle changes that can accelerate the loss of a few pounds without risking your health. Among these, perhaps the most well-known is increasing protein intake so that the body burns fat and does not lose muscle mass. It is also effective to drink green tea because of its caffeine or to reduce the consumption of starchy and floury dishes.”
Protein intake
Protein is particularly good for weight loss. As mentioned previously, increasing the intake of this macronutrient will elevate the Thermic Effect of Food. It is also crucial to building lean muscle mass. Protein also helps lower food cravings and regulate appetite.
Dietary supplements
Countless dietary supplements claim to help you lose weight. They tend to be sold as ‘metabolism boosters’ and ‘fat burners’, promising amazing results in no time. But are they actually able to speed up your weight loss? In most cases, there is no evidence they can deliver on the promise. But that does not mean that every supplement is a waste of money.
Many weight loss supplements contain high doses of caffeine. And according to a meta-analysis published in the Critical Reviews in Food Science and Nutrition, for every doubling in the caffeine intake, the reduction in weight, BMI, and fat mass may increase almost twofold. This is because this compound increases thermogenesis, and, unsurprisingly, increases your energy levels during workouts.
However, it is important to maintain a reasonable intake of caffeine, particularly if you are sensitive to it. As stated in the Sports Medicine journal, ingestion of 3–9 mg/kg of body weight approximately 60 min prior to exercise is the recommended way to power up your workout. That could be in the form of caffeinated drinks, or dietary supplements.
Another dietary supplement worth considering is a green tea extract. As reported in the Critical Reviews in Food Science and Nutrition, green tea compounds (such as caffeine and catechins) can increase thermogenesis and increase fat lipolysis.
However, not every green tea supplement is produced to the same standard. Multiple studies have shown that those containing doses of EGCG (Epigallocatechin gallate) between 100 and 460 mg a day have shown the best effects on body fat and body weight reduction in trials lasting more than 12 weeks.
This article is for informational purposes only and is not meant to offer medical advice.
Anna Gora is a health writer at Live Science, having previously worked across Coach, Fit&Well, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a Bachelor's degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.