There was great diversity in the patterns of weight loss over the first year the Look AHEAD intensive multifactorial intervention, despite its common protocol and goals. Of the eight baseline characteristics considered, seven had significant relationships with the magnitudes of the month-to-month weight loss and/or the trajectory of weight loss. The principal component analysis allowed these associations to be succinctly described.
Both patterns of response to the first year of the intervention predicted successful maintenance of weight loss after four years. Greater month-to-month weight loss accumulation and more gradual and sustained weight loss during the first year were each associated with better longer term weight loss. These associations were independent of each other and of a panel of participant characteristics: markers of demography, health, and lifestyle, including baseline body mass index and diabetes control.
Many authors have stressed the importance that the initial magnitude of weight loss has for longer term success with behavioral interventions (12
). A separate analysis of Look AHEAD data found that year 1 weight loss was the strongest determinant of year 4 weight loss, accounting for 22% of its overall variability (7
). The Diabetes Prevention Program found that achieving an initial 7% weight loss strongly predicted longer term weight loss (16
Several authors have found that losing weight more gradually is associated with greater long term maintenance of weight loss (17
), however others have not (19
). A complexity in this discussion is that the rate of initial weight loss is often not differentiated from the overall weight loss. Toubro, et al. attempted to examine this experimentally, using different intervention approaches to vary the rate of weight loss while achieving similar longer-term overall levels (20
). They found that more rapid weight losses were associated with slightly better maintenance. This approach differs from our analyses in that we examine rates of response to a common intervention. The principal components analysis distinguished the timing of year 1 weight loss from its overall accumulation. Both independently were important predictors of longer term maintenance of weight loss. A weight loss that is achieved through gradual and sustained increments, rather than a more rapid loss weight loss that is not sustained, is associated with better long term maintenance, perhaps reflecting both the rate and the maintenance of adopting lifestyle changes during the first year.
Greater month-to-month weight losses during the first year of the weight loss intervention was associated with longer term benefits in markers of diabetes control, blood pressure control, and lipid control, independent of current weight loss. The factors that were most strongly associated with year 1 weight losses – HbA1c, HDL-cholesterol, and systolic blood pressure – have all been shown to be influenced by the overall Look AHEAD intervention relative to its control condition (9
) and to be influenced by weight loss interventions of shorter duration (21
). It may be that early success in losing weight serves to mark a group of individuals who are better able to maintain their health long term, however covariate adjustment for a number of personal characteristics did not materially alter these associations.
Importantly, the magnitude of month-to-month weight losses during the first year of the intervention was associated with improved HbA1c, systolic blood pressure, and HDL-cholesterol even after controlling for weight changes from baseline to the time that these outcomes were assessed. These associations could not be explained by changes in medications nor by a number of other factors that might be related to overall adherence and medical care. It is possible that this is an example of a “legacy” effect, i.e. an intervention effect that is carried forward that is not explained fully by current measures (22
). Another possibility is that, due to short-term fluctuations in weight, a measurement at a single point does not fully capture associations between weight change and health outcomes that have emerged over time.
Whether or not weight losses during the first year were gradual and sustained or early with slight regain did not appear to have marked longer term influence on markers of health, with or without adjustment for year 4 weight status. It may be that the differences in longer term weight gain that are associated with the trajectory of initial weight loss are less meaningful and can be largely overcome with medical management and continued lifestyle intervention.
There are several qualifications to the findings. Patterns in weight loss with individual components have not been linked to targets of the intervention (behavioral strategies, physical activity, change in fitness, use of meal replacements, orlistat, etc.) and it is possible that these may be variously associated with weight loss patterns and with longer term outcomes. Findings are based on the Look AHEAD intervention and adults with type 2 diabetes who were eligible and volunteered for a clinical trial: it is possible that they will not generalize to other settings or groups.
The associations that are described between weight loss patterns over the initial year of a long-term intervention stress the importance of the initial success of the intervention. While current weight status is the strongest predictor of outcomes, individuals who were most responsive to the intervention (i.e. those who accumulated greater month-to-month weight losses during the first year) tended to have better longer term outcomes in addition to what could be predicted from their current weight. Individuals with more gradual and sustained weight losses during the first year had longer term better weight loss maintenance, but this pattern produced no additional benefits on the health outcomes we assessed.