This study's principal finding was that an ILI induced a clinically significant weight loss in all subsets of a demographically and ethnically diverse population. Although a statistically significant difference in weight loss was observed between men and women (as expected), the absolute difference was small, and both genders achieved clinically significant reductions. The study's oldest participants (65–74 years) achieved significantly greater weight losses than the two younger age groups, but all three groups were within 1.5% of each other (with mean losses ranging from 7.9 to 9.4%). Similarly, African-American and Hispanic participants lost significantly less weight than non-Hispanic whites, consistent with findings from other multisite trials (5,6,7). However, weight losses achieved in this study are among the largest reported for either African-American or Hispanic participants, demonstrating the wide-scale acceptability of Look AHEAD's lifestyle intervention. American Indian/other participants achieved a mean loss of 5.5% which, while smaller than that of other ethnicities, is still sufficiently large to engender improvements in cardiovascular risk factors (2,16).
Participants' weight losses were related to their adherence to the study's treatment recommendations. Of the three measures of adherence, physical activity correlated most strongly with weight loss, accounting for 16.1% of the variance, as determined by multiple regression analysis. Participants in the highest quartile of self-reported physical activity lost 11.9% of initial weight, compared with only 4.4% for those in the lowest quartile. More frequent attendance at treatment sessions and greater consumption of meal replacements also were associated with greater weight loss, although to a lesser degree than physical activity (as determined by the regression analysis).
The design of this study prevents us from concluding that adherence to any of the three treatment factors caused greater weight loss. For example, participants who achieved high levels of physical activity may have done so because they had lost more weight (and felt more comfortable exercising), rather than activity causing their weight loss. However, randomized trials (32,33), as well as observational studies (34), have reported a positive relationship between weight loss and high levels of physical activity. In addition to burning calories, increased physical activity may contribute to weight management by sparing the loss of fat-free mass or by facilitating dietary adherence by controlling appetite and improving mood (35). Randomized trials similarly have shown that meal replacements increase weight loss, compared with the consumption of a self-selected diet of conventional foods with the same calorie goal (20,21,22). Liquid meal replacements and other portion-controlled approaches appear to facilitate patients' adherence to their prescribed calorie targets (20,21,22,23,24). Controlled trials also have shown that the more treatment sessions participants are provided, the more weight they lose (35). Greater weight loss probably results from strengthening adherence to diet and activity recommendations, as suggested by the robust intercorrelations among the three measures in this study.
Differences in weight loss among some of the study's demographic groups appeared to be explained by differences in treatment adherence. Thus, the significantly greater weight losses observed in men than women and in the study's oldest participants (65 to 74 years) appeared to result from their greater treatment attendance, minutes of physical activity, and consumption of meal replacements. The analyses suggest that women would have lost as much weight as men, and younger participants as much as older ones, if they had adhered as closely to the study's treatment recommendations. By contrast, the significantly greater weight loss observed in non-Hispanic white participants, as compared with African Americans and Native Americans, was not eliminated by controlling for differences in physical activity, treatment attendance, and consumption of meal replacements. Smaller weight losses in these latter two groups could have been attributable to a variety of nontreatment-related factors. African-American women, for example, were found in previous studies to have a lower resting energy expenditure than age- and weight-matched non-Hispanic white women (36,37) and to have greater reductions in resting energy expenditure in response to weight loss (38,39), each of which could limit weight loss.
We note that the significantly lower treatment attendance of America Indian/other participants may have reflected significant economic barriers (e.g., lack of transportation) known at the study's outset. In addition, their lower reported minutes of physical activity and consumption of meal replacements are also likely a consequence of their attending fewer treatment sessions and, thus, having fewer opportunities to report their activity and food intake. Moreover, we believe that the data reported here underestimate physical activity and meal replacement use for all participants. If participants forgot to record these events in their diaries, or failed to submit a diary for a given week, they received a value of 0 for the number of minutes of physical activity for the week (as well as for the number of meal replacements consumed).
In addition to underscoring the importance of treatment adherence, the results of this study offer two other practical findings. The first is that insulin users can achieve clinically significant weight loss by participating in a comprehensive weight loss intervention (10,11,12). Although insulin users lost ∼2% less weight than participants who took no diabetes medications, the more important finding was that patients on insulin still lost an impressive 7.4% of initial weight. The second finding is that persons 65–74 years of age appear to be acceptable candidates for weight loss trials, from which they now are frequently excluded. The oldest participants in this study were model citizens, in terms of their treatment adherence. Their achieving the largest weight losses of the three age groups confirms findings from the Diabetes Prevention Program (5). Older individuals may have more time and fewer barriers to participating than their younger counterparts. Analysis of body composition, however, is needed to ensure that the greater weight loss in older individuals was not attributable to a greater loss of lean tissue or bone (40).
Despite the lifestyle intervention's clear strengths, we note three limitations, the first of which is that the ILI participants were highly motivated and were provided intensive treatment, free of charge. Thus, the generalizability of the present findings to primary care practice is not known. Second, participants in ILI were weighed at each treatment visit by unmasked intervention staff, and these data were included in this report. To fully understand the treatment effects, the reader should use these data in conjunction with weight data obtained by masked study staff (on all participants) at outcome visits. A third limitation is that nearly one-third of ILI participants did not achieve a 5% reduction initial weight, a benchmark of clinically significant weight loss (16). During the first 6 months, these participants had significantly poorer adherence to the study's treatment recommendations than did those who lost ≥5% of initial weight. The use of orlistat by 291 of the former participants, during the second 6 months of treatment, increased weight loss only marginally, in contrast to expected reductions (29). There has been little research in weight management on methods to assist suboptimal or nonresponders. Over time, Look AHEAD will provide a rich data set with which to examine the effects of different “rescue” interventions for the induction or maintenance of weight loss.
In summary, an intensive group lifestyle intervention induced a mean loss of 8.6% of initial weight in overweight and obese participants with type 2 diabetes. The intervention was clinically effective in all subsets of an ethnically and demographically diverse population. Greater self-reported physical activity and consumption of meal replacements, as well as more frequent treatment attendance, were associated with greater weight loss. Study efforts are currently devoted to helping participants maintain their lost weight to have the best opportunity to determine whether intentional weight loss reduces cardiovascular mortality and morbidity.
This report represents a further analysis of the first year weight losses in the Look AHEAD study. It was prepared by the authors on behalf of the Look AHEAD Research Group. Members of the research group who participated in the recruitment, assessment, treatment, and retention of participants during the first year of the study are shown below:
The Johns Hopkins Medical Institutions: Frederick L. Brancati, MD, MHS (Principal Investigator); Jeff Honas, MS (Program Coordinator); Lawrence Cheskin, MD (Co-investigator); Jeanne M. Clark, MD, MPH (Co-investigator); Kerry Stewart, EdD (Co-investigator); Richard Rubin, PhD (Co-investigator); Jeanne Charleston, RN; Kathy Horak, RD.
Pennington Biomedical Research Center: George A. Bray, MD (Principal Investigator); Kristi Rau (Program Coordinator); Allison Strate, RN (Program Coordinator); Brandi Armand, LPN (Program Coordinator); Frank L. Greenway, MD (Co-investigator); Donna H. Ryan, MD (Co-investigator); Donald Williamson, PhD (Co-investigator); Amy Bachand; Michelle Begnaud; Betsy Berhard; Elizabeth Caderette; Barbara Cerniauskas; David Creel; Diane Crow; Helen Guay; Nancy Kora; Kelly LaFleur; Kim Landry; Missy Lingle; Jennifer Perault; Mandy Shipp, RD; Marisa Smith; Elizabeth Tucker.
The University of Alabama at Birmingham: Cora E. Lewis, MD, MSPH (Principal Investigator); Sheikilya Thomas MPH (Program Coordinator); Monika Safford, MD (Co-investigator); Vicki DiLillo, PhD; Charlotte Bragg, MS, RD, LD; Amy Dobelstein; Stacey Gilbert, MPH; Stephen Glasser, MD; Sara Hannum, MA; Anne Hubbell, MS; Jennifer Jones, MA; DeLavallade Lee; Ruth Luketic, MA, MBA, MPH; Karen Marshall; L. Christie Oden; Janet Raines, MS; Cathy Roche, RN, BSN; Janet Truman; Nita Webb, MA; Audrey Wrenn, MAEd.
Harvard Center: Massachusetts General Hospital. David M. Nathan, MD (Principal Investigator); Heather Turgeon, RN, BS, CDE (Program Coordinator); Kristina Schumann, BA (Program Coordinator); Enrico Cagliero, MD (Co-investigator); Linda Delahanty, MS, RD (Co-investigator); Kathryn Hayward, MD (Co-investigator); Ellen Anderson, MS, RD (Co-investigator); Laurie Bissett, MS, RD; Richard Ginsburg, PhD; Valerie Goldman, MS, RD; Virginia Harlan, MSW; Charles McKitrick, RN, BSN, CDE; Alan McNamara, BS; Theresa Michel, DPT, DSc CCS; Alexi Poulos, BA; Barbara Steiner, EdM; Joclyn Tosch, BA. Joslin Diabetes Center. Edward S. Horton, MD (Principal Investigator); Sharon D. Jackson, MS, RD, CDE (Program Coordinator); Osama Hamdy, MD, PhD (Co-investigator); A. Enrique Caballero, MD (Co-investigator); Sarah Bain, BS; Elizabeth Bovaird, BSN, RN; Ann Goebel-Fabbri, PhD; Lori Lambert, MS, RD; Sarah Ledbury, MEd, RD; Maureen Malloy, BS; Kerry Ovalle, MS, RCEP, CDE. Beth Israel Deaconess Medical Center. George Blackburn, MD, PhD (Principal Investigator); Christos Mantzoros, MD, DSc (Co-investigator); Kristinia Day, RD; Ann McNamara, RN.
University of Colorado Health Sciences Center: James O. Hill, PhD (Principal Investigator); Marsha Miller, MS, RD (Program Coordinator); JoAnn Phillipp, MS (Program Coordinator); Robert Schwartz, MD (Co-investigator); Brent Van Dorsten, PhD (Co-investigator); Judith Regensteiner, PhD (Co-investigator); Salma Benchekroun MS; Ligia Coelho, BS; Paulette Cohrs, RN, BSN; Elizabeth Daeninck, MS, RD; Amy Fields, MPH; Susan Green; April Hamilton, BS, CCRC; Jere Hamilton, BA; Eugene Leshchinskiy; Michael McDermott, MD; Lindsey Munkwitz, BS; Loretta Rome, TRS; Kristin Wallace, MPH; Terra Worley, BA.
Baylor College of Medicine: John P. Foreyt, PhD (Principal Investigator); Rebecca S. Reeves, DrPH, RD (Program Coordinator); Henry Pownall, PhD (Co-investigator); Ashok Balasubramanyam, MBBS (Co-investigator); Peter Jones, MD (Co-investigator); Michele Burrington, RD; Chu-Huang Chen, MD, PhD; Allyson Clark, RD; Molly Gee, MEd, RD; Sharon Griggs; Michelle Hamilton; Veronica Holley; Jayne Joseph, RD; Patricia Pace, RD: Julieta Palencia, RN; Olga Satterwhite, RD; Jennifer Schmidt; Devin Volding, LMSW; Carolyn White.
University of California at Los Angeles School of Medicine: Mohammed F. Saad, MD (Principal Investigator); Siran Ghazarian Sengardi, MD (Program Coordinator); Ken C. Chiu, MD (Co-investigator); Medhat Botrous; Michelle Chan, BS; Kati Konersman, MA, RD, CDE; Magpuri Perpetua, RD.
The University of Tennessee Health Science Center: University of Tennessee East. Karen C. Johnson, MD, MPH (Principal Investigator); Carolyn Gresham, RN (Program Coordinator); Stephanie Connelly, MD, MPH (Co-investigator); Amy Brewer, RD, MS; Mace Coday, PhD; Lisa Jones, RN; Lynne Lichtermann, RN, BSN; Shirley Vosburg, RD, MPH; and J. Lee Taylor, MEd, MBA. University of Tennessee Downtown. Abbas E. Kitabchi, PhD, MD (Principal Investigator); Helen Lambeth, RN, BSN (Program Coordinator); Debra Clark, LPN; Andrea Crisler, MT; Gracie Cunningham; Donna Green, RN; Debra Force, MS, RD, LDN; Robert Kores, PhD; Renate Rosenthal PhD; Elizabeth Smith, MS, RD, LDN; and Maria Sun, MS, RD, LDN; and Judith Soberman, MD (Co-investigator).
University of Minnesota: Robert W. Jeffery, PhD (Principal Investigator); Carolyn Thorson, CCRP (Program Coordinator); John P. Bantle, MD (Co-investigator); J. Bruce Redmon, MD (Co-investigator); Richard S. Crow, MD (Co-investigator); Scott Crow, MD (Co-investigator); Susan K Raatz, PhD, RD (Co-investigator); Kerrin Brelje, MPH, RD; Carolyne Campbell; Jeanne Carls, MEd; Tara Carmean-Mihm, BA; Emily Finch, MA; Anna Fox, MA; Elizabeth Hoelscher, MPH, RD, CHES; La Donna James; Vicki A. Maddy, BS, RD; Therese Ockenden, RN; Birgitta I. Rice, MS, RPh CHES; Tricia Skarphol, BS; Ann D. Tucker, BA; Mary Susan Voeller, BA; Cara Walcheck, BS, RD.
St. Luke's Roosevelt Hospital Center: Xavier Pi-Sunyer, MD (Principal Investigator); Jennifer Patricio, MS (Program Coordinator); Stanley Heshka, PhD (Co-investigator); Carmen Pal, MD (Co-investigator); Lynn Allen, MD; Diane Hirsch, RNC, MS, CDE; Mary Anne Holowaty, MS, CN.
University of Pennsylvania: Thomas A. Wadden, PhD (Principal Investigator); Barbara J. Maschak-Carey, MSN, CDE (Program Coordinator); Stanley Schwartz, MD (Co-investigator); Gary D. Foster, PhD (Co-investigator); Robert I. Berkowitz, MD (Co-investigator); Henry Glick, PhD (Co-investigator); Shiriki K. Kumanyika, PhD, RD, MPH (Co-investigator); Johanna Brock; Helen Chomentowski; Vicki Clark; Canice Crerand, PhD; Renee Davenport; Andrea Diamond, MS, RD; Anthony Fabricatore, PhD; Louise Hesson, MSN; Stephanie Krauthamer-Ewing, MPH; Robert Kuehnel, PhD; Patricia Lipschutz, MSN; Monica Mullen, MS, RD; Leslie Womble, PhD, MS; Nayyar Iqbal, MD.
University of Pittsburgh: David E. Kelley, MD (Principal Investigator); Jacqueline Wesche-Thobaben, RN, BSN, CDE (Program Coordinator); Lewis Kuller, MD, DrPH (Co-investigator); Andrea Kriska, PhD (Co-investigator); Janet Bonk, RN, MPH; Rebecca Danchenko, BS; Daniel Edmundowicz, MD (Co-investigator); Mary L. Klem, PhD, MLIS (Co-investigator); Monica E. Yamamoto, DrPH, RD, FADA (Co-investigator); Barb Elnyczky, MA; George A. Grove, MS; Pat Harper, MS, RD, LDN; Janet Krulia, RN, BSN, CDE; Juliet Mancino, MS, RD, CDE, LDN; Anne Mathews, MS, RD, LDN; Tracey Y. Murray, BS; Joan R. Ritchea; Jennifer Rush, MPH; Karen Vujevich, RN-BC, MSN, CRNP; Donna Wolf, MS.
The Miriam Hospital/Brown Medical School: Rena R. Wing, PhD (Principal Investigator); Renee Bright, MS (Program Coordinator); Vincent Pera, MD (Co-investigator); John Jakicic, PhD (Co-investigator); Deborah Tate, PhD (Co-investigator); Amy Gorin, PhD (Co-investigator); Kara Gallagher, PhD (Co-investigator); Amy Bach, PhD; Barbara Bancroft, RN, MS; Anna Bertorelli, MBA, RD; Richard Carey, BS; Tatum Charron, BS; Heather Chenot, MS; Kimberley Chula-Maguire, MS; Pamela Coward, MS, RD; Lisa Cronkite, BS; Julie Currin, MD; Maureen Daly, RN; Caitlin Egan, MS; Erica Ferguson, BS, RD; Linda Foss, MPH; Jennifer Gauvin, BS; Don Kieffer, PhD; Lauren Lessard, BS; Deborah Maier, MS; JP Massaro, BS; Tammy Monk, MS; Rob Nicholson, PhD; Erin Patterson, BS; Suzanne Phelan, PhD; Hollie Raynor, PhD, RD; Douglas Raynor, PhD; Natalie Robinson, MS, RD; Deborah Robles; Jane Tavares, BS.
The University of Texas Health Science Center at San Antonio: Steven M. Haffner, MD (Principal Investigator); Maria G. Montez, RN, MSHP, CDE (Program Coordinator); Carlos Lorenzo, MD (Co-investigator).
University of Washington/VA Puget Sound Health Care System: Steven Kahn MB, ChB (Principal Investigator); Brenda Montgomery, RN, MS, CDE (Program Coordinator); Robert Knopp, MD (Co-investigator); Edward Lipkin, MD (Co-investigator); Matthew L. Maciejewski, PhD (Co-investigator); Dace Trence, MD (Co-investigator); Terry Barrett, BS; Joli Bartell, BA; Diane Greenberg, PhD; Anne Murillo, BS; Betty Ann Richmond, MEd; April Thomas, MPH, RD.
Southwestern American Indian Center, Phoenix, Arizona and Shiprock, New Mexico: William C. Knowler, MD, DrPH (Principal Investigator); Paula Bolin, RN, MC (Program Coordinator); Tina Killean, BS (Program Coordinator); Cathy Manus, LPN (Co-investigator); Jonathan Krakoff, MD (Co-investigator); Jeffrey M. Curtis, MD, MPH (Co-investigator); Justin Glass, MD (Co-investigator); Sara Michaels, MD (Co-investigator); Peter H. Bennett, MB, FRCP (Co-investigator); Tina Morgan (Co-investigator); Shandiin Begay, MPH; Bernadita Fallis RN, RHIT, CCS; Jeanette Hermes, MS, RD; Diane F. Hollowbreast; Ruby Johnson; Maria Meacham, BSN, RN, CDE; Julie Nelson, RD; Carol Percy, RN; Patricia Poorthunder; Sandra Sangster; Nancy Scurlock, MSN, ANP-C, CDE; Leigh A. Shovestull, RD, CDE; Janelia Smiley; Katie Toledo, MS, LPC; Christina Tomchee, BA; Darryl Tonemah PhD.
University of Southern California: Anne Peters, MD (Principal Investigator); Valerie Ruelas, MSW, LCSW (Program Coordinator); Siran Ghazarian Sengardi, MD (Program Coordinator); Kathryn Graves, MPH, RD, CDE; Kati Konersman, MA, RD, CDE; Sara Serafin-Dokhan.
Wake Forest University: Mark A. Espeland, PhD (Principal Investigator); Judy L. Bahnson, BA (Program Coordinator); Lynne Wagenknecht, DrPH (Co-investigator); David Reboussin, PhD (Co-investigator); W. Jack Rejeski, PhD (Co-investigator); Alain Bertoni, MD, MPH (Co-investigator); Wei Lang, PhD (Co-investigator); Gary Miller, PhD (Co-investigator); David Lefkowitz, MD (Co-investigator); Patrick S. Reynolds, MD (Co-investigator); Paul Ribisl, PhD (Co-investigator); Mara Vitolins, DrPH (Co-investigator); Michael Booth, MBA (Program Coordinator); Kathy M. Dotson, BA (Program Coordinator); Amelia Hodges, BS (Program Coordinator); Carrie C. Williams, BS (Program Coordinator); Jerry M. Barnes, MA; Patricia A. Feeney, MS; Jason Griffin, BS; Lea Harvin, BS; William Herman, MD, MPH; Patricia Hogan, MS; Sarah Jaramillo, MS; Mark King, BS; Kathy Lane, BS; Rebecca Neiberg, MS; Andrea Ruggiero, MS; Christian Speas, BS; Michael P. Walkup, MS; Karen Wall, AAS; Michelle Ward; Delia S. West, PhD; Terri Windham.
Central Resources Centers
DXA Reading Center, University of California at San Francisco: Michael Nevitt, PhD (Principal Investigator); Susan Ewing, MS; Cynthia Hayashi; Jason Maeda, MPH; Lisa Palermo, MS, MA; Michaela Rahorst; Ann Schwartz, PhD; John Shepherd, PhD.
Central Laboratory, Northwest Lipid Research Laboratories: Santica M. Marcovina, PhD, ScD (Principal Investigator); Greg Strylewicz, MS.
ECG Reading Center, EPICARE, Wake Forest University School of Medicine: RonaldJ. Prineas, MD, PhD (Principal Investigator); Teresa Alexander; Lisa Billings; Charles Campbell, AAS, BS; Sharon Hall; Susan Hensley; Yabing Li, MD; Zhu-Ming Zhang, MD.
Diet Assessment Center, University of South Carolina, Arnold School of Public Health, Center for Research in Nutrition and Health Disparities: Elizabeth J Mayer-Davis, PhD (Principal Investigator); Robert Moran, PhD.
Hall-Foushee Communications, Inc.: Richard Foushee, PhD; Nancy J. Hall, MA.
National Institute of Diabetes and Digestive and Kidney Diseases: Barbara Harrison, MS; Van S. Hubbard, MD PhD; Susan Z.Yanovski, MD.
National Heart, Lung, and Blood Institute: Lawton S. Cooper, MD, MPH; Jeffrey Cutler, MD, MPH; Eva Obarzanek, PhD, MPH, RD.
Centers for Disease Control and Prevention: Edward W. Gregg, PhD; David F. Williamson, PhD; Ping Zhang, PhD.
Funding and Support
This study is supported by the Department of Health and Human Services through the following cooperative agreements from the National Institutes of Health: DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57154, DK57178, DK57219, DK57008, DK57135, and DK56992. The following federal agencies have contributed support: National Institute of Diabetes and Digestive and Kidney Diseases; National Heart, Lung, and Blood Institute; National Institute of Nursing Research; National Center on Minority Health and Health Disparities; Office of Research on Women's Health; and the Centers for Disease Control and Prevention. This research was supported in part by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases. Additional support was received from The Johns Hopkins Medical Institutions Bayview General Clinical Research Center (M01RR02719); the Massachusetts General Hospital Mallinckrodt General Clinical Research Center (M01RR01066); the University of Colorado Health Sciences Center General Clinical Research Center (M01RR00051) and Clinical Nutrition Research Unit (P30 DK48520); the University of Tennessee at Memphis General Clinical Research Center (M01RR0021140); the University of Pittsburgh General Clinical Research Center (M01RR000056 44) and NIH grant (DK 046204); and the University of Washington/VA Puget Sound Health Care System Medical Research Service, Department of Veterans Affairs; Frederic C. Bartter General Clinical Research Center (M01RR01346). The following organizations have committed to make major contributions to Look AHEAD: Federal Express; Health Management Resources; Johnson & Johnson, LifeScan Inc.; Optifast-Novartis Nutrition; Roche Pharmaceuticals; Ross Product Division of Abbott Laboratories; Slim-Fast Foods Company; and Unilever.