It’s no secret. The world is getting fatter. The obesity rate has been climbing for decades and it doesn’t appear to be stopping anytime soon. What is similarly concerning are the statistics on weight maintenance. Many are able to successfully lose weight, but very few are able to keep this weight off long-term, further facilitating the current crisis. It has been reported that as little as 15-20% of those who lose weight are able to sustain their loss over multiple years (1,2).
To combat this statistic, it is commonly proposed that slower rates of weight loss are superior for long-term weight loss maintenance (3). The rationale is that with a slower rate of loss, changes in lifestyle and diet are more gradual, and as consequence, are more likely to be permanent. Thus, the individual will not revert back to their unhealthy ways and regain the weight they originally lost.
This belief seems to have emerged as a reaction to nutritionally insufficient very-low-calorie diets in the 1960s and has since been propagated for over half a century (4). To this day, it is commonly recommended to not exceed 1-2 lbs of weight loss per week (5). Many textbooks echo this proclamation, with some reporting rates of weight loss greater than 2 lbs per week as dangerous, and that a rate of loss less than 1 lb per week may be ideal for obesity treatment (4).
What Does the Data Actually Say?
In a study titled “The association between rate of initial weight loss and long-term success in obesity treatment: does slow and steady win the race?” (6), participants were encouraged to consume 1,200 kcal per day and to increase physical activity to reach 10,000 steps per day for six months.
Following this intervention, subjects took part in a 12-month follow-up program involving contact twice per month in the form of group sessions, telephone contact, or newsletters. In this program, subjects were instructed to maintain their new eating and exercise habits.
For the data analysis, the participants were divided into groups based on their rate of weight loss during the initial intervention. The FAST group lost more than 1.5 lbs per week, the MODERATE group lost more than 0.5 lbs per week but less than 1.5 lbs, and the SLOW group lost less than 0.5 lbs per week.
The results displayed that from baseline to 18 months, weight changes in the FAST, MODERATE, and SLOW groups were -10.9, -7.1, and -3.7 kg, respectively. At 18 months, 50.7% of participants in the FAST group, 35.6% of participants in the MODERATE group, and 16.9% of participants in the SLOW group maintained a clinically significant 10% reduction in body weight.
In accordance, a paper titled “Evaluation of early weight loss thresholds for identifying non-responders to an intensive lifestyle intervention” found similar outcomes (7). In this study, data from the Look AHEAD trial was evaluated. It featured 2,327 participants who underwent an intensive lifestyle intervention. Participants were prescribed a calorie goal of 1200-1800 kcal per day (depending on their initial body weight) and advised to consume <30% of total calories from dietary fat.
The analysis showed that 50.1% of individuals achieving a ≥ 2% weight loss at month one attained a ≥ 10% weight loss at year one, whereas only 15.2% of those who had a weight loss <2% at month one reached the milestone. In addition, it was found that the higher the initial weight loss, the greater the proportion of participants who were successful at year one. These results can likely be explained by the fact that those who achieved a greater initial weight loss were motivated by their progress. The motivation generated by this rapid success led to improved dietary adherence, and thus, augmented long-term outcomes.
These findings are in line with previous research which suggest that greater initial weight loss and very-low-energy diets are associated with superior weight-loss maintenance (8,9).
In another study titled “The effect of rate of weight loss on long-term weight management: a randomised controlled trial”, subjects were randomized to either a rapid weight loss program, which included 450-800 kcal per day for 12 weeks, or a gradual weight loss program, which featured a typical 400-500 kcal deficit for 36 weeks (10). The intervention was then followed by a weight maintenance phase. In phase 2, for 144 weeks, participants were instructed to follow an individualized diet for weight maintenance.
The results reported that 76 of the 94 rapid weight loss participants achieved 12.5% or more weight loss, compared with 53 of 85 gradual weight loss participants. By week 144 of phase 2, average weight regain was 10.4 kg in the gradual weight loss group and 10.3 kg in rapid weight loss group. Despite vastly different dietary interventions, in the end, weight regain was virtually identical between conditions.
What is particularly interesting about this study is that significantly more participants discontinued the gradual weight loss program (18%) than the rapid weight loss program (3%). The main reason for withdrawal was difficulty adhering to the diet. This phenomenon may be explained by a lack of motivation to adhere to the diet due to lackluster progress.
Lastly, in an experiment titled “The effect of rate of weight loss on long-term weight regain in adults with overweight and obesity”, participants were randomly assigned to a 12-week low-calorie diet of 1,250 kcal per day or a five week very low-calorie diet of 500 kcal per day (11). The end goal for each group was a weight loss of 10% of body weight.
The weight loss period resulted in similar body weight changes in the slow weight loss group and rapid weight loss group (-8.2 +/- 0.5 kg vs. -9.0 +/- 0.4 kg), with an average weight loss of 0.7 kg/week and 1.8 kg/week, respectively. In the nine month follow-up period, mean weight regain was 4.2 kg in the low-calorie diet group and 4.5 kg in the very low-calorie diet group. Again, despite very different rates of weight loss, weight regain was nearly identical between groups.
Take Home Message
All diets work, and they work because they reduce calorie intake. The issue does not lie in the specific diet selected, but how it suits the unique lifestyle and preferences of the user. If you have 20 lbs to lose, a 4-6 very-low-calorie diet is just as viable (if not superior) to a conservative energy deficit for 16-20 weeks. Despite what many self-proclaimed “evidence-based practitioners” might proclaim, very-low-calorie diets are in fact safe when performed under professional supervision (12). Further, the rate of weight loss during a diet is not a predictor of future weight regain.
The real issue is in the exit strategy, or lack thereof, as most diets don’t provide this crucial information on what to do when the weight loss goal is achieved and the diet is over. The energy intake and physical activity levels required to lose weight are much different than what is required to maintain weight. Following the weight loss phase, these adjusted figures need to be established and adhered to prevent weight regain.
- Wing RR, Phelan S. Long-term weight loss maintenance. The American journal of clinical nutrition. https://www.ncbi.nlm.nih.gov/pubmed/16002825. Published July 2005. Accessed June 4, 2019.
- Ayyad C, Andersen T. Long-term efficacy of dietary treatment of obesity: a systematic review of studies published between 1931 and 1999. Obesity reviews : an official journal of the International Association for the Study of Obesity. https://www.ncbi.nlm.nih.gov/pubmed/12119984. Published October 2000. Accessed June 4, 2019.
- Myths, Presumptions, and Facts about Obesity | NEJM. New England Journal of Medicine. https://www.nejm.org/doi/full/10.1056/NEJMsa1208051. Published January 31, 2013. Accessed June 4, 2019.
- Casazza K, Brown A, Astrup A, et al. Weighing the Evidence of Common Beliefs in Obesity Research. Critical reviews in food science and nutrition. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4272668/. Published December 6, 2015. Accessed June 4, 2019.
- Position of the Academy of Nutrition and Dietetics: Interventions for the Treatment of Overweight and Obesity in Adults. eat right. https://jandonline.org/article/S2212-2672(15)01636-6/pdf. Published 2016. Accessed June 4, 2019.
- Nackers LM, Ross KM, Perri MG. 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. https://www.ncbi.nlm.nih.gov/pubmed/20443094. Published September 2010. Accessed June 4, 2019.
- Unick JL, Hogan PE, Neiberg RH, et al. Evaluation of early weight loss thresholds for identifying nonresponders to an intensive lifestyle intervention. Obesity (Silver Spring, Md.).
- Astrup A, Rössner S. Lessons from obesity management programmes: greater initial weight loss improves long‐term maintenance. Obesity Reviews. https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1467-789x.2000.00004.x?sid=nlm:pubmed. Published December 25, 2001. Accessed June 4, 2019.
- Anderson JW, Konz EC, Frederich RC, Wood CL. Long-term weight-loss maintenance: a meta-analysis of US studies. The American journal of clinical nutrition. https://www.ncbi.nlm.nih.gov/pubmed/11684524. Published November 2001. Accessed June 4, 2019.
- Purcell K, Sumithran P, Prendergast L, Bouniu C, Delbridge E, Proietto J. The effect of rate of weight loss on long-term weight management: a randomised controlled trial. The Lancet Diabetes & Endocrinology. https://www.thelancet.com/journals/landia/article/PIIS2213-8587(14)70200-1/fulltext. Published October 2014. Accessed June 2019.
- Vink RG, Roumans NJT, Arkenbosch LAJ, Mariman ECM, van Baak MA. The effect of rate of weight loss on long-term weight regain in adults with overweight and obesity. Obesity (Silver Spring, Md.). https://www.ncbi.nlm.nih.gov/pubmed/26813524. Published February 2016. Accessed June 4, 2019.
- Sumithran P, Proietto J. Safe year-long use of a very-low-calorie diet for the treatment of severe obesity. The Medical journal of Australia. https://www.ncbi.nlm.nih.gov/pubmed/18341463. Published March 17, 2008. Accessed June 4, 2019