You’re supposed to lose weight “slow and steady,” aren’t you?  Everyone knows that losing weight faster does bad things to your body and increases the chances of weight regain, right?  Maybe not.  If you look closely at the science, you see it’s not that simple. In fact, losing weight faster might help you keep it off better…

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Does losing weight faster at the start of a diet increase the risk of regaining that weight? The short answer is no, not according to science.

Cutting calories too much can have negative effects on your body, and the majority of dieters do gain back weight, but faster weight loss in the beginning doesn’t look like it increases the risk of regain.

Most of the current research says there’s no difference in long term maintenance success between those who lose it faster at first and those who lose it slower.

In fact, there’s evidence showing the opposite. Some studies found that a large initial weight loss as the first step in a longer term weight management program decreased the chances of dropout during the weight loss phase, and increased the odds of maintaining the weight loss afterwards.

The long answer is a little more complicated because there are lots of variables involved, including what’s your definition of “fast” weight loss?

If someone started out with unrealistic expectations for weight loss, and we told them to set goals to lose it slower, we’d be doing them a favor (helping them avoid muscle loss, fatigue, hunger, and disappointment).

But if we made a blanket statement and told everyone they should lose weight slower, it might actually interfere with some people’s long term success. That’s because the ideal rate of weight loss can vary from person to person, and getting off to a good start appears to be helpful for just about everyone.

Why Do Most People Believe Slower Is Always Better?

If you were thinking that slower weight loss is always better, you wouldn’t be alone. The majority of health-minded people, including fitness pros, believe that in the long run, slow weight loss is superior to any kind of rapid weight loss plan.

I’ve also seen recommendations for slow weight loss and realistic goals published for years by national health organizations, in trainer certification manuals, and in nutrition textbooks.

The fear of and movement away from faster weight loss probably started back in the 1970s when large numbers of people tried very low calorie crash diets. The Last Chance Diet was the most notorious. The book sold 2.5 million copies, and introduced the liquid diet concept to the world. It also killed more than 60 people.

The liquid “nutrition” products were so bad, (made from low quality collagen protein and animal by-products) and the program so poorly designed, it didn’t even provide the essential vitamins, minerals, fatty acids, and amino acids a person needs to maintain lean mass and stay healthy. The result was malnutrition, muscle wasting, heart problems, and death.

Very low calorie weight loss programs, including liquid plans (as low as 500 to 800 per day), still exist and they’re sometimes even prescribed by doctors. But the dangers aren’t what they were in the old days. With physician supervision and modern, higher-quality supplements, they may take weight off fast for obese patients when it’s desperately needed, while providing enough nutrition to maintain health.

Why else is fast weight loss frowned on so much? Another reason is it seems like common sense to avoid extreme diets not only because they’re strict and unpleasant but also because if they don’t teach behavior and lifestyle change, they’re only seen as a temporary fix. It’s a popular belief that if you don’t start learning good nutrition and lifestyle behaviors from day one, and start turning them into habits, you’re more likely to gain back the weight later.

Obviously, we should never do anything dangerous, we don’t want quick fixes, and “slow and steady” is a good health and fitness philosophy for sustainability over the long haul. But when it comes to the rate of weight loss, it’s not accurate to say, “slower is always better” and “faster is always worse.” For starters, what does fast and slow weight loss even mean? If it’s not defined, that will be a major cause for confusion.

What Is “Fast” And “Slow” Weight Loss?

If you look at standard recommendations by trusted health and fitness organizations, the most common guideline is to aim for dropping 1 or 2 pounds a week. Some people consider that slow, especially only a pound a week, but that belief is mainly a product of reality TV, tabloids, infomercials and other weight loss marketing and media that makes it look slow in comparison to the testimonials.

Looking at weight loss ads or Biggest Loser results are terrible ways to set standards or define what is fast or slow weight loss. By any sensible or scientific standard, an average loss of 1.5 to 2 pounds a week is terrific success, and even just a pound a week, lost consistently, is solid progress for many people (that’s 52 pounds in a year!)

More than that, it’s scientifically logical to suggest aiming for 1 to 2 pounds of fat loss per week because that only requires a 500 to 1000 calorie per day reduction below maintenance and most people can easily handle that, given the amount of calories they burn each day. To aim for 3 or 4 pounds a week – which is fast weight loss by any reasonable standard – would require a 1500 to 2000 calorie per day deficit. That amount of restriction is not easy to sustain. In some cases, it’s not possible.

What if you’re a shorter, smaller person and your maintenance level is only 2000 calories per day? That would mean to lose 4 pounds per week, you’d have to eat nothing for a week, which is why it’s not possible, practically speaking. To lose 3 pounds per week would mean you’d only get to eat 500 calories per day, which is possible, but not sustainable or advisable for long.

So you see, it makes good sense why so many common weight loss guidelines don’t recommend shooting for much more than 2 pounds per week for ongoing weight loss.

But on the other hand, not everyone burns only 2000 calories per day. Most men burn closer to 2500 to 2700 per day and the larger and more active an individual is – male or female – the more calories they have to work with.

A large, heavy (overweight or obese) person might easily burn 3000 to 3500 calories per day or even more if active, so a 1500 to 2000 calorie per day deficit looks more feasible in that scenario.

Men will generally be able to lose weight faster than women. Larger, taller and heavier people of either gender will be able to lose faster. Highly active individuals will also burn more and therefore be able to lose more. It’s also worth remembering that some people can tolerate lower calories better than others, regardless of their size or weight.

For a small person, we might say 1.5 pounds a week is fast weight loss. For a big person who is overweight, 1.5 pounds a week might seem modest and 2.5 to 3 pounds a week would be considered fast. Incidentally, another common guideline for setting weekly weight loss goals that’s individualized is 1% of total body weight, so at 300 pounds that would be 3 pounds a week.

If you’re not clear in your mind about what fast or slow weight loss means, as well as what’s biologically possible given your daily calorie expenditure, then knowing what’s a realistic, achievable, and healthy goal can stay confusing, and popular recommendations won’t always make sense. In addition, our big question – what’s better in the long run, slower or faster weight loss – will be impossible to answer.

Before we do tackle that question, there’s one more thing to consider. What is fast or slow weight loss also depends on when the weight is lost: In the first week of the diet, the first month, or three to six months in? Those are different animals.

Early weight loss is the easiest (and fastest). Sustained weight loss usually gets harder and slower as the months go by, and don’t forget that as you lose weight, you become a smaller person, so you burn fewer calories each day for that reason alone. Stated differently, as you lose weight, your calorie deficit automatically gets smaller.

Initial Weight Loss Versus Ongoing Weight Loss

Everyone has heard stories of dramatic rapid weight loss, but most come in the form of personal testimonials, including from outliers, which don’t represent typical real world situations where most of us can get guidance. The rest of the rapid weight loss anecdotes we hear are usually short-term results from the initial phase of a weight loss program.

It’s not uncommon to see weight losses of 4, 5, or 6 pounds in the first week, and even 8 to 10 pounds is not unheard of, especially when someone is very heavy and their new diet of choice is low in carbs. Higher than average rates of weight loss often continue into the second week before starting to level off to a more normal ongoing rate.

Obviously, the majority of a huge initial weight loss is going to be water weight (and glycogen), not body fat. Weight loss is not the same as fat loss. This isn’t necessarily a bad thing – the big scale drop may be quite motivating – but it’s an important distinction to make when you’re setting ongoing weight loss goals. If you’re including water weight, fast weight loss in the beginning is quite normal.

It’s rare, however, to see even a 3 pound per week weight loss sustained for any length of time, and even 2.5 pounds a week is pretty “fast” if you’re looking at long-term weight loss research statistics. Ongoing weight loss at rates above 3 to 3.5 pounds per week are uncommon and arguably, unrealistic for most people to expect.

For all these reasons above, this explains why 1 to 2 pounds a week of ongoing weight loss is considered “slow and steady” and is often given as a realistic goal, and anything above that is considered fast.

Now with that long explanation of “what’s slow and what’s fast” out of the way, that brings us back to the original question: Is it advisable to drop weight fast in the beginning, or will that make something bad happen that causes weight regain in the long run?

To help us answer, let’s turn to the research.

Early Studies Said Slow Weight Loss (With Small Calorie Deficits) Is Better Maintained

Another reason why it’s so widely believed that it’s best to lose weight slowly is because older research said so.

For example, in several studies, obese and overweight subjects were given fairly small reductions in calories – between 1500 and 2200 calories per day for women, and between 1900 and 2600 calories per day for men. After 16 weeks, they achieved modest weight losses, and another 12 weeks later, they had still kept it off.

In a similar study, obese women were prescribed 1800 calories per day – a small calorie reduction – and they too achieved a modest loss of body weight and were less susceptible to regain after the follow up period, compared to a group that only ate 1200 calories per day.

These early results looked like evidence in favor of “lose it slow and steady.” But when the studies started getting longer, that’s when people started to wonder if fast early weight loss wasn’t so bad after all.

In one study that lasted a full year (52 weeks), the researchers found the amount of weight lost during the 12-week weight loss phase was the best predictor of what the total weight loss would be for the following 40 weeks.

Because the data was now conflicting, the subject of fast versus slow weight loss became controversial and more research became a priority. Scientists started calling for better and longer studies with follow-up periods spanning 18 months, or even 2 to 3 years (which is not easy or cheap to do), as well as randomized trials that could help determine cause and effect instead of correlation only.

Well-Designed Long-Term Study Says “Faster” Weight Loss Is Actually Better

An 18 month study at the University of Florida found that people who lost weight the most quickly in the first month achieved the greatest total weight loss during the weight loss phase. The fast weight loss group was also no more likely to regain weight after a year and a half than the moderate and slow weight loss groups. Once again this went against the popular belief that slower is better.

There was a catch though. The fast weight loss group only lost 1.5 pounds per week in the first month and a total of 29.7 pounds in 6 months (averaging out to 1.2 pounds per week). The researchers called that “fast” weight loss, but this study doesn’t really tell us that fast weight loss, as most people define it, is better in the long run.

It did however, tell us that the group that lost the fastest (1.5 pounds per week) in the first month had better long term results than the moderate group that lost between .5 and 1.5 pounds per week, and the moderate group did better than the slow group that only lost .5 pounds per week or less.

Some fair conclusions to draw from this study would be that good results in the first month may improve the long term success rate, and losing weight faster, but still within normal recommendations, does not increase the risk of regaining the weight.

What About Even Lower Calories And Even Faster Weight Loss? Does That Make You More Likely To Regain?

In the scientific research, moderate calorie restriction is considered 1500 to 1800 calories a day, low calorie diets come in around 1200 calories per day, and very low calorie diets are only 500 to 800 calories per day (these numbers may vary slightly, as men usually need more calories than women).

Normally, a good nutrition coach would not recommend very low calorie diets for many reasons, including worries about sustainability, muscle loss, and regaining the weight. But as mentioned earlier, for obese patients, physicians sometimes do prescribe them, with supervision, counseling, and supplementation. Scientists have studied the effects of very low calorie diets as well.

In 2016, a study from the Netherlands took 57 overweight men and women and randomized them into two groups – very low calories (500 per day for 5 weeks) for fast weight loss, and low calories (1250 per day for 12 weeks) for slow weight loss. At the end of the diet phase (5 or 12 weeks respectively), there was a 4 week weight stable period and then a 9 month follow up. Weight and body composition were measured before and after each period.

The weight loss was similar in both groups – 18 pounds for the slow group versus 19.8 pounds for the fast group. The difference of course, was that the fast weight loss group lost it in only 5 weeks (3.9 pounds a week), while the slow weight loss group lost it in 12 weeks (1.5 pounds per week).

As we always expect (unfortunately), both groups started regaining weight afterwards. But here was the key finding: the rate of weight loss did not affect the amount of weight regain. Within the 9-month follow up period, both groups had regained more than 50% of the weight they had lost – but it was about the same amount. The old traditional belief would have predicted that people doing a 500-calorie liquid diet for 5 weeks who lost weight more than twice as fast would regain it faster, or regain more, but that didn’t happen.

An even longer study from The University of Melbourne Australia found something similar. This time the fast group ate 450 to 800 calories per day for 12 weeks and the gradual group ate 400 to 500 calories under their maintenance level for 36 weeks. Afterwards, there was a 144 week follow up, so the entire study was three years long.

Once again, both groups lost about the same amount of weight – 32 pounds versus 31.2 – but the slow group took three times longer. That’s 2.67 pounds per week for the fast group versus .87 pounds per week for the gradual group (definitely “slow and steady” in that gradual group).

Again, both groups started regaining the lost weight when their respective weight loss phases ended. By the end of the three year period, more than 70% of participants from both groups had regained most of the weight.

The relapse rates are a bit disheartening and multi-year maintenance is still a big challenge for everyone. But the fact that faster initial weight loss – even with very low calorie diets – did not make relapse worse is well worth noting. To look at the bright side, 30% of the subjects had kept the weight off after 3 years, and half of those people lost the weight quickly.

Why We Still Don’t Widely Recommend Very Low Calorie Fast Weight Loss Diets

At this point, a few hardy souls who aren’t afraid of very low calories might be thinking, “Well hot damn, I should eat 500 to 800 calories a day and try to lose weight faster!” The problem is, many of these types of diets have risks that include fatigue, constipation, and gallstones, among others. All the major health and weight loss associations agree that very low calorie diets should be used sparingly, for short durations, under medical supervision, and when intensive lifestyle modification can also be given.

An even more worrisome side effect was also discovered in the Australian study. As you might have guessed, the very low calorie groups lost lean body mass. And here’s the nail in the coffin: in this study, and in previous studies, losing lean mass did correlate with greater weight regain (not to mention, losing muscle means you end up with a weaker and softer body).

In some cases, the loss of lean tissue was minimal and might be argued a small price to pay for an obese person to drop a lot of fat quickly. But very low calorie diets are especially incompatible for people training for a better physique, and when you’re already lean and trying to get leaner, the risk of muscle loss is much higher than when you’re obese. This is one of the reasons that most bodybuilders and physique athletes keep calorie deficits small and intentionally aim to lose no more than a pound a week.

On top of that, most people find eating only 500 to 800 calories a day pretty miserable. Fatigue, hunger, and food cravings are part of what makes it hard to sustain. Two of the only reasons some people say it’s tolerable are that if the macros are low in carbs, they sometimes end up in ketosis, which may suppress their appetite, and drinking liquid protein means the diet is simple and there is nothing much to think about (in the way of macros, food choices, meal planning and so on).

One more reason most people should pass on very low calorie diets is that research subjects eating in the 500 to 800 calorie range did lose more weight in the beginning, but there was no long term advantage compared to groups that followed low calorie diets at 1200-1250 per day. Ultimately, they ended up in the same place, the very low calorie dieters (“fast” group) simply hit their weight loss goal sooner.

Very low calorie diets and excessively fast weight loss can have negative consequences. But on the other hand, the data from these studies adds more evidence to the argument that faster initial weight loss – at least in the reasonable amounts we’ve discussed here – doesn’t cause faster weight regain.

This research also suggests that diets with slightly more aggressive calorie deficits, but that are still nutritionally adequate, might have a useful role to “kick start” weight loss more quickly for some people if that’s their desire, and that this is not necessarily a bad idea as it has long been believed.

Caveats And Cautions

Losing muscle is always one of the risks of losing weight too quickly. Obese people are less likely to lose muscle in a large calorie deficit than lean people, but since losing lean mass is linked to weight regain, every dieter should be on guard and take steps to avoid this pitfall.

It’s worth noting that many studies about fast weight loss and long-term success may not have included resistance training and some of them only measured weight loss, not body composition. It’s well-known that resistance training is vital for maintaining muscle when losing weight in a calorie deficit.

It’s also well-established that exercise and a high overall activity level is one of the most important keys to long term weight loss maintenance. This means that whether a person is training during the weight loss phase, and keeps up their exercise regimen after the weight loss phase can have a huge impact not only on whether they reach their goal but also whether they keep the weight off long term.

People who stop exercising and lead sedentary lifestyles after weight loss are almost 100% certain to regain weight. A high level of physical activity after weight loss may be the “make you or break you” factor for long-term maintenance, not how fast the weight is lost.

For people who wish to attempt losing weight faster, in addition to weight training, it’s critical to consume enough protein during the weight loss phase. This includes making sure calories are not so low that the ideal protein intake can’t even be reached.

Adequate protein while in a calorie deficit, especially large deficits, can be the difference between losing lean body mass or not. Protein can also help suppress appetite. This is one of the reasons that when calories are prescribed at a very low level, a very high proportion of the calories typically comes from protein. (This is sometimes called a protein-sparing modified fast or PSMF).

In addition, one of the reasons there may not have been a higher amount of regain in some studies even after fast initial weight loss on very low calorie diets, is that the diets were prescribed in combination with intensive nutrition education and behavior modification programs to help with compliance and to guide the transition into maintenance.

People who don’t have ongoing support or don’t receive any counseling on nutrition, exercise, and lifestyle change – they simply follow a diet that’s handed to them on their own – may not get the same results or have the same long term success rate. This is especially true if the diets are extremely low in calories or only use supplements.

Even when doctor-prescribed, if only supplements are used during the weight loss phase without any counseling, that kind of diet program doesn’t give any education on how to eat real food for long-term health and weight management.

It’s a common belief that if you don’t start learning good nutrition habits from day one and if you don’t use the weight loss phase to practice and strengthen those habits, then this will raise the risk of weight regain later. It does appear however, based on the research, that even short-term very low calorie diets can work as long as nutrition and lifestyle counseling is given for transitioning into the normal eating phase.

Why Does Faster Initial Weight Loss Seem To Improve Long Term Success?

So now we’re left with one last burning question: Exactly why does faster weight loss in the initial phase seem to produce equal or better long term results without increasing risk of relapse?

The reason for the greater total weight loss is obvious – if you lose more weight in the first month or so, as long as you keep going at a steady rate, even if it slows down, you’ll end up with a greater total weight loss because of that early head start.

The most logical explanation for the equal or even better long-term success, including with maintenance, is also simple and straightforward: Starting a diet, and then seeing immediate results from your efforts is motivating and reinforcing.

When the reward comes immediately after the behavior change, it reinforces the behavior and increases the desire to keep putting in more effort. When the weight starts coming off right away, it can also increase self efficacy – it makes you think, “Hey, I can do this” and it turns into a repeating and self-reinforcing positive cycle of motivation and action.

On the other hand, a very slow rate of initial weight loss may be a de-motivator. To take action and to feel like you’re working hard at something yet not seeing much result may lead to early drop out or less effort in the future. A negative attitude develops and the lack of results makes you think, “Why bother?”

Persistence and patience are not qualities that the majority of people naturally have in large amounts, and delaying gratification is a difficult thing to do. Trying to get off to a good start is simply working in harmony with human nature and psychology.

Depending on a person’s starting weight, disposition, and ability to tolerate lower calories, going “all in” with a stricter diet (bigger deficit) or harder effort right from the start could be a perfectly viable and successful approach – even though this runs contrary to the slow and steady mindset most people promote.

The Bottom Line

Some people might interpret all of this as, “lose weight as fast as you can.” That would be a dangerous oversimplification. The ideal goal is always fat loss, not just weight loss, and there is only so much body fat you can burn each week, practically and even biologically speaking. Realistic goal setting is always important.

Trying to exceed normal achievable rates of fat loss will only result in fatigue, lower performance, mental fog and even serious health problems. If larger than predicted weight loss actually is achieved, we could argue it’s either a neutral or negative outcome if it came from loss of water or lean body mass.

It’s important for this reason to understand what achievable rates of weight loss are, including how this number may not be the same for everyone (bigger people lose faster) or the same at every time (everyone can lose faster in the beginning).

However, it is possible that some people could increase their rate of weight loss, and understanding what science really says about losing weight at a faster rate, they could pursue the faster loss without worrying about higher risk of relapse. It may be particularly beneficial when done at the start of a new diet.

It’s probably even fair to say that faster weight loss is always better than slower weight loss if the weight lost is pure fat, no lean body mass is sacrificed, energy and performance are not diminished, and the weight is lost safely, healthfully and without causing undue hunger or hardship.

There is also nothing wrong with slow as long as it’s also steady. The important thing is that you’re making progress and you appreciate your progress so you stay motivated. It’s also worth remembering that even if weight loss is your number one goal and you’re not a bodybuilder or athlete, training can be a huge boon to your motivation because while you can’t see a difference on the scale every day, you can measure progress in the gym every single day.

In conclusion, scientific evidence says losing weight faster at the start of a diet does not increase the risk of regaining the weight later. The idea that rapid initial weight loss leads to more rapid weight regain can indeed be officially placed in the myth category.

– Tom Venuto,
Author of Burn the Fat, Feed the Muscle

60-Second Summary:

1. Most people believe that “slow and steady” is better for weight loss success. Most people also believe that losing weight too quickly increases the risk of weight regain. Early research seemed to confirm this.

2. The latest research, including studies lasting up to three years, found that losing weight quickly at the start of a diet does not increase the risk of weight regain. The idea that faster initial weight loss leads to faster weight regain is now considered a myth.

3. Studies found that even diets as low as 500 to 800 calories per day still did not increase the risk of regain. However, very low calorie diets come with downsides, including risk of muscle loss, hunger, and fatigue.

4. By all reasonable standards, 1 to 2 pounds of weight loss per week is successful and is a common recommendation. Most people consider a weekly loss of .5 to 1 pound slow, 2 pounds moderate, and 3 pounds or more fast.

5. In most of the research, “slow” weight loss was typically .8 to 1.5 pounds per week and “fast” weight loss was typically 2.6 to 3.9 pounds per week.

6. Faster weight loss is only better up to a point. To choose realistic goals, it’s important to know how much fat the human body can burn in a week. Beyond that, additional weight loss will only be water and lean body mass.

7. A calorie deficit is required to lose body fat. Based on what’s realistic given body size, goals, preference, and hunger tolerance, dieters may choose a smaller deficit and eat more food to lose weight more slowly, or they can choose a larger deficit and eat less food to lose weight more quickly.

8. Some people can lose weight faster because they can more easily achieve a larger deficit. This depends mainly on body size as well as activity level. A short, petite, inactive person will never lose weight as fast as a tall, heavy, active person. Rates of weight loss are relative and may vary – what’s slow for some people is fast for others.

9. Excessive calorie restriction or diet tactics that lead to muscle loss can undermine long-term results and increase risk of weight regain.

10. It appears that losing weight faster (inside the range of what’s realistic for each person) in the beginning stage of a diet is helpful for sustained motivation and for positive reinforcement of behavior and habits.

11. Getting off to a poor start, or losing weight extremely slow can be de-motivating. Some studies found a higher dropout rate for people who lost weight slowly in the beginning compared to people who lost it faster.

12. It’s reasonable and may be beneficial to diet a little harder/stricter in the beginning, knowing that faster weight loss out of the gate won’t be harmful as long as goals are realistic and no unhealthy tactics are used.

Scientific References:

Astrup A, Lessons from obesity management programs: greater initial weight loss improves long-term maintenance, Obesity reviews, 1, 17-19, 2000.

Casazza K et al, Myths, Presumptions and facts about obesity, New England Journal of Medicine, 368:6, 446-454, 2013.

Damoon Ashtary-Larky, et al, Rapid Weight Loss vs. Slow Weight Loss: Which is More Effective on Body Composition and Metabolic Risk Factors? Int J Endocrinol Metab. 15:3, e13249, 2017.

Jeffery R et al, Are smaller weight losses or more achievable weight loss goals better in the long term for obese patients? J Consult Clin Psychol. 66:4, 641-645. 1998

Lutes L et al, Small changes in nutrition and physical activity promote weight loss and maintenance: 3-month evidence from the ASPIRE randomized trial. Ann Behav Med, 35, 351-357, 2008.

Nackers L, The association between rate of initial weight loss and long-term success in obesity treatment: Does slow and steady win the race? International Journal of Behavioral Medicine, 17(3), 161-167, 2010. University of Florida.

Purcell K et al, The effect of rate of weight loss on long-term weight management: a randomized controlled trial, Lancet Diabetes Endocrinology, 2:12, 954-962, 2014.

Sbrocco T et al, behavioral choice treatment promotes continuing weight loss: preliminary results of a cognitive-behavioral decision-based treatment for obesity. J Consult Clin Psychol. 67, 260-266, 1999.

Vink R et al, The effect of rate of weight loss on long-term weight regain in adults with overweight and obesity, Obesity, 24:2, 321-327, 2016.

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