Outcomes Research in Review

Slow and Steady May Not Win the Race for Weight Loss Maintenance

Vink RG, Roumans NJ, Arkenbosch LA, et al. The effect of rate of weight loss on long-term weight regain in adults with overweight and obesity. Obesity (Silver Spring) 2016;24:321–7.


 

References

Study Overview

Objective. To compare weight regain after rapid versus slower loss of an equivalent amount of weight.

Study design . Randomized clinical trial.

Setting and participants . This study took place in a single medical center in the Netherlands. Investigators recruited 61 adults (no age range provided) with body mass index (BMI) between 28–35 kg/m 2 and at a stable weight (no change of > 3 kg for the past 2 months) to participate in a weight loss study. Individuals with type 2 diabetes, dyslipidemia, uncontrolled hypertension, or liver, heart or kidney disease were excluded, as were those who were currently pregnant or reported consuming more than moderate amounts of alcohol.

Once consented, participants were randomized into one of 2 study arms. The rapid weight loss arm was prescribed a very-low-calorie diet (VLCD) with just 500 kcal/day (43% protein/43% carb/14% fat) for 5 weeks, after which they transitioned to a 4-week “weight stable” period, and then a 9-month follow-up period (overall follow-up time of ~11 months; 10 months after weight loss). In contrast, the slower weight loss arm was prescribed a low-calorie diet (LCD) with 1250 kcal/day (29% protein/48% carb/23% fat) for 12 weeks, after which they also transitioned to a 4-week weight stable period and 9 months of follow-up (overall follow-up time of ~13 months; 10 months after weight loss). VLCD (rapid weight loss) participants received 3 meal replacement shakes per day (totaling 500 kcal) during the weight loss period and were also told they could consume unlimited amounts of low-calorie vegetables. The LCD (slower weight loss) participants received 1 meal replacement shake per day during their 12 weeks of weight loss and were responsible for providing the remainder of their own meals and snacks according to guidelines from a study dietitian. Following active weight loss, both groups then shifted to higher-calorie, food-based diets during a “weight stable” 4-week period and were responsible during this time for providing all of their own food. The researchers do not specify the details of the diet composition for this weight stable period. Exposure to the registered dietitian was the same in both groups, with 5 consultations during weight loss (weekly for VLCD, presumably more spaced out for LCD) and 4 during weight stable period. No further diet advice or meal replacement support was given during the 9-month follow-up period, but participants came in for monthly weigh-ins.

Main outcome measure . The primary outcome measure was change in weight (ie, amount of weight regained) during the 9-month follow-up period, compared between groups using an independent samples t test. Additional biometric measures included change in waist circumference and changes in body composition. For the latter, the researchers used a “Bod Pod” to conduct air-displacement plethysmography and determine what percentage of an individual’s weight was fat mass (FM) versus lean mass/water (FFM [fat-free mass]). They then compared the amount of FFM lost between groups, again using the independent samples t test.

The researchers also collected information on self-reported physical activity (questionnaire) and self-reported history of weight cycling (number of times a participant had previously lost and regained at least 5 kg) prior to this study. These were not outcomes per-se, but were collected so that they could be examined as correlates of the biometric outcomes above, using Pearson and Spearman’s correlation coefficients.

Results. The LCD ( n = 29) and VLCD ( n = 28) groups were similar at baseline with no significant differences reported. Of the 61 individuals initially enrolled, 57 (93%) completed the study. Summary statistics are reported only for these 57 individuals. No imputation or other methods for handling missing data were used. There were slightly more women than men in the study (53% women); the average (SD) age was 51.8 (1.9) years in the LCD group and 50.7 (1.5) years in the VLCD group. Mean starting BMI was 31 kg/m 2 (31.3 [0.5] in LCD, 31.0 [0.4] in VLCD) and both groups had just under 40% body fat at baseline (39.9% [1.8] in LCD, 39.7% [1.5] in VLCD).

After 12 weeks of weight loss for LCD, or 5 weeks of weight loss for VLCD, both groups lost a similar amount of total weight (8.2 [0.5] kg in LCD vs. 9.0 [0.4] kg in VLCD), then had no significant changes in weight during the subsequent 4-week “weight stable” period. However, during the weight stable period VLCD patients had an average 0.8 (0.6) cm increase in waist circumference (a rebounding after a decrease of 7.7 cm during weight loss), while LCD patients on average had a continued decrease of 1.0 (0.5 cm) in waist circumference ( P = 0.003).

There was no significant difference between groups for the primary outcome of weight regain during 9-months of follow-up (4.2 [0.6] kg regained for LCD, 4.5 [0.7] for VLCD; P = 0.73). The only significant correlates of weight regain were amount of FFM lost (more lean mass lost predicted more weight regain), and amount of physical activity reported during follow-up (more activity predicted less regain). Participant sex, age, starting BMI, history of weight cycling, and amount of weight lost did not correlate with rate of re-gain.

One area where there was a significant between-group difference, both after initial weight loss and persisting after the weight stable period, was in the amount of FFM lost (a rough approximation of lost lean mass, eg, muscle mass). VLCD participants had more FFM loss (1.6 [0.2] kg) than LCD participants (0.6 [0.2] kg) ( P < 0.01) after active weight loss, and continued to have significantly more FFM loss (0.8 [0.2] kg vs. 0.2 [0.2] kg) after the 4-week weight stable period.

There were no between-group differences at the end of weight loss or at the end of follow-up for hip or waist circumference or for blood pressure.

Conclusion. The authors conclude that rate of weight loss does not affect one’s risk of weight regain after a diet, after a similar amount of weight has been lost.

Commentary

The failure of most diets to produce durable weight loss is a frustration for patients, clinicians, and researchers. In general, regardless of the composition of a diet, the majority of patients will regain some or all of their lost weight within several years after completing the diet. The reasons for weight regain are complex, and include reversion to old eating or physical activity behaviors but also a strong physiologic drive by the body to reverse weight loss that it perceives as a threat to health [1].

One area in diet research that has recently generated some controversy is whether or not rate of initial weight loss might impact a patient’s ability to maintain that weight loss, with the conventional wisdom (and national guidelines, in some cases), suggesting that slower weight loss is preferable to rapid weight loss for this reason [2]. A handful of studies have challenged this notion, however, and suggested that rapid weight loss does not necessarily lead to greater weight regain [3,4]. Previous such studies, however, have not generally been designed to compare regain after equal amounts of weight loss, which may make their results more difficult to interpret.

The present study contributes another piece of evidence to the argument that rapid initial weight loss may not increase a patient’s risk of regain. This small randomized trial is timely and has several features that make it a unique contribution. First, the design of the study allowed for both groups, despite losing weight at very different rates, to reach the same amount of total weight loss before being followed forward in time. This made weight regain much easier to compare between groups during follow-up. Second, the study included measurement of changing body composition—ie, what kind of weight was being lost (fat vs. fat-free mass)—rather than just the total amount of weight. This allowed the researchers to present data for an outcome that is mechanistically related to metabolic rate (and therefore weight regain), and one that might have implications for longer-term health after rapid versus more moderate-pace weight loss.

Several aspects of the study design, however, may limit the impact of the findings. For example, in both arms, while a certain type of diet was “prescribed,” there is no comment about assessment of participant fidelity to the prescribed diet, and there is potential for very different levels of adherence between groups, especially in active weight loss, when basically all meals were provided to the VLCD arm, but LCD subjects were responsible for about 90% of their own meals. This could have led to larger discrepancies between prescribed and actual diet in the LCD arm relative to VLCD. Granted, the rate of weight loss was the exposure of interest, and that clearly varied between groups as expected, implying at least moderate fidelity to prescribed caloric content of each diet, but how much protein vs. fat vs. carb was actually consumed by each group is not clear. Additionally, while 9 months of post weight-loss follow-up is certainly a good start in terms of follow-up duration, it may not have been sufficient to observe differences that would later emerge between the groups for weight regain. Other long-term weight loss maintenance studies have followed patients for several years or longer after initial weight loss [5].

Using data from all participants, the researchers reported that the amount of FFM an individual lost was a predictor of weight regain during follow-up. This finding is in keeping with the idea that more lean mass loss leads to lower metabolic rate and predisposes to weight regain (hence the conventional wisdom to avoid rapid weight loss with low-protein diets). In keeping with this theme, VLCD patients, whose protein intakes and activity levels were lower, did lose more FFM (ie, lean mass) than LCD patients. It was therefore surprising that in between-group analyses there was no statistical difference in weight regain. On some level, this raises concerns about the robustness of the overall finding. Perhaps with a larger sample, more precise measures of FFM lost (eg, with DEXA scanning instead of the “bod pod” or longer follow-up, this difference in lost lean mass between groups actually would have predicted greater weight regain for VLCD patients. The researchers attribute some of the FFM loss after the caloric restriction phase to decreased water and glycogen stores, rather than muscle mass, and speculate that this is why no impact on weight regain was seen between groups.

From a generalizability standpoint, there are important safety concerns with the use of VLCDs, aside from subsequent risk of weight regain, that are not addressed with this study. Many patients simply cannot tolerate a 500 kcal per day diet, including those with more severe obesity (who have higher daily energy requirements) or those with complicated chronic medical conditions who might be at higher risk of complications from such low energy intake. Accordingly, these kinds of patients were not included in this study, so it is not clear whether results might generalize to them.

Applications for Clinical Practice

Despite the conventional wisdom that slower weight loss may be more sustainable over time, several recent trials have suggested otherwise. Nonetheless, rapid weight loss produced with the use of VLCDs is not appropriate for every patient and must be carefully overseen by a weight management professional. Furthermore, rapid weight loss may place patients at increased risk of preferentially losing lean mass, which does correlate with risk of weight regain and could set them up for other health problems in the long-term. More studies are needed in this area before a definitive judgment can be made regarding the long term risks and benefits of rapid versus moderate-pace weight loss.

—Kristina Lewis, MD, MPH

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