Conventional wisdom says that if you lose weight quickly that weight typically won’t stay off.
In fact, people often wonder why they end up regaining weight after weight loss.
There’s a certain amount of logic to that perspective.
Typically, fast weight loss means that you don’t have time to develop new and healthy behaviors.
Additionally, the types of diets that lead to fast weight loss are often not sustainable in the long-term.
There are also other reasons why fast weight loss might make it harder to keep weight off, such as the fact that people often lose muscle mass along with fat.
But, there hasn’t been that much research conducted that looks at regaining weight after weight loss.
One very recent and very interesting study looked at the impact that rate of weight loss had on weight regain.
The Study Itself
The study involved the use of a dietary intervention. Participants were randomized into two groups for the intervention.
One group followed a low-calorie diet for 12 weeks. This was considered the slow weight loss group.
The other group followed a very low-calorie diet for 5 weeks. This was considered the fast weight loss group.
After the diet, participants then maintained their weight for 4 weeks and were followed up after 9 months on a maintenance diet.
Participants also had access to a dietitian throughout the study and the 4-week stable period, but not during the subsequent maintenance period.
At the end of the maintenance period, the amount of weight regain between the two groups looked like this.
The slow weight loss group did regain less weight overall (9.3 pounds versus 9.9), but the difference between them wasn’t significant.
The authors did also note that the process of fast weight loss did reduce levels of lean muscle mass.
That is an undesirable approach and suggests that slower weight loss is more beneficial if you want to maintain your lean body mass.
That loss of lean mass did also contribute to a higher amount of weight regain for the fast weight loss group. However, that impact was small, so it did not affect the overall outcome of the study.
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Limitations of the Study
This study was really interesting and one of the first studies I have seen on this specific topic.
But, it did have some pretty major limitations as well.
Issue #1: Fast versus Slow Weight Loss
One issue with this study is the definitions of fast and slow weight loss.
In the study, the fast weight loss group lost an average of just under 4 pounds per week, while the slow weight loss group lost around 1.5 pounds per week.
Would you call 4 pounds a week fast weight loss?
You might, but someone else wouldn’t.
Realistically, refining fast versus slow weight loss is a very subjective task.
For example, there is a diet called the 3 day military diet that claims you can lose 10 pounds per week.
The outcomes of the study don’t offer any indication of whether someone on that type of diet would gain weight back more quickly or not.
Issue #2: Diet Type
The study only considered low and very low-calorie diets.
There are a lot of different types of diets out there and they don’t impact the body in the same way.
Fad diets are a great example of this.
Fad diets often result in fast weight loss because they involve extreme conditions or because they trick the body in some way.
But, the nature of the diet makes them difficult or impossible to sustain in the long-term.
That type of diet may be more likely to promote weight regain than a very low-calorie diet is.
Issue #3: Using a Maintenance Diet
In general, the conventional idea that fast weight loss contributes to weight regain is connected to the idea of yo-yo dieting.
With yo-yo dieting, people typically follow a diet for a while and then stop it – often once they have lost the weight.
But, they soon regain that weight, which leads to another round of dieting.
That is an exceptionally common pattern, especially when people lose weight fast as they diet.
As I mentioned earlier, one of the reasons for this may be that people don’t develop healthy patterns when they lose weight fast.
So, when they stop following their diet, they immediately revert back to their unhealthy habits. In turn, this can contribute to weight gain.
The experimental protocol for this study placed people on one of two maintenance diets following their weight loss.
As such, their calorie consumption was still constrained even after the fast weight loss.
In doing this, the authors of the study clearly showed that it is not fast weight loss itself that contributes to weight regain.
However, their conclusions do not rule out the potential role that changes in behavior could have.
Issue #4: The Study Population
The authors were very specific in who was part of the study and the final selection included 57 individuals.
One interesting requirement was that participants had to have a stable weight for 2 months prior to the study.
To me, this suggests that the people in the study had, at least, some control over their diet and their weight.
Because of this, the group might be less likely to regain weight following a diet than a more average group of participants.
The population was also entirely Caucasian, had an average age of around 50 and an average weight of around 200 pounds.
Having a population like that is important for this type of study as it helps reduce potential differences between participants.
But, at the same time, the population limits the conclusions that can be drawn from the study.
So, the observed effects might not be true for people who were heavier (or lighter), were younger or were from a different racial background.
Implications of the Study
This study does show that fast weight loss itself doesn’t promote weight regain, at least within the conditions of the study.
This means that you could effectively lose weight through a very low-calorie diet, as long as you followed it up with a maintenance diet.
But, the authors don’t answer the more general question of whether fast weight loss can lead to regaining weight after weight loss.
Based on the results of the study, I think it is likely that the biological aspects of fast weight loss don’t have any impact on weight regain.
However, the psychological and behavioral impacts of fast weight loss may well promote weight regain.
Want to Lose Weight and Keep it Off?
Weight loss is a huge industry, with no shortage of bold claims. But, long-term weight loss doesn’t come from a crash diet or a popular fad. Instead, it is connected to sustainable habits and healthy foods.
Check out my most recommended products and guides to see where you can get started.
What do you think? Does fast weight loss affect your ability to keep the weight off?