DIABETICMedicine DOI: 10.1111/dme.12500

Research: Educational and Psychological Issues Long-term changes in dietary and food intake behaviour in the Diabetes Prevention Program Outcomes Study L. M. Jaacks1, Y. Ma2, N. Davis3, L. M. Delahanty4, E. J. Mayer-Davis1,5, P. W. Franks6, J. Brown-Friday3, M. Isonaga7, A. M. Kriska8, E. M. Venditti8 and J. Wylie-Rosett3 for the Diabetes Prevention Program Research Group 1 Department of Nutrition, University of North Carolina, Chapel Hill, NC, 2George Washington University, Washington, DC, 3Albert Einstein College of Medicine, Bronx, NY, 4Massachusetts General Hospital and Harvard Medical School, Boston, MA, 5Department of Medicine, University of North Carolina, Chapel Hill, NC, 6 €, Sweden and Harvard School of Public Health, Boston, MA, 7University of Hawaii, Honolulu, HI, and 8University of Pittsburgh, Pittsburgh, Lund University, Malmo PA, USA

Accepted 9 May 2014

Abstract Aims To compare change in dietary intake, with an emphasis on food groups and food intake behaviour, over time across treatment arms in a diabetes prevention trial and to assess the differences in dietary intake among demographic groups within treatment arms. Methods Data are from the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study. Participants were randomized to a lifestyle intervention (n = 1079), metformin (n = 1073) or placebo (n = 1082) for an average of 3 years, after which the initial results regarding the benefits of the lifestyle intervention were released and all participants were offered a modified lifestyle intervention. Dietary intake was assessed using a food frequency questionnaire at baseline and at 1, 5, 6 and 9 years after randomization.

Compared with the metformin and placebo arms, participants in the lifestyle arm maintained a lower total fat and saturated fat and a higher fibre intake up to 9 years after randomization and lower intakes of red meat and sweets were maintained for up to 5 years. Younger participants had higher intakes of poultry and lower intakes of fruits compared with their older counterparts, particularly in the lifestyle arm. Black participants tended to have lower dairy and higher poultry intakes compared with white and Hispanic participants. In the lifestyle arm, men tended to have higher grain, fruit and fish intakes than women.

Results

Conclusions Changes in nutrient intake among participants in the lifestyle intervention were maintained for up to 9 years. Younger participants reported more unhealthy diets over time and thus may benefit from additional support to achieve and maintain dietary goals.

Diabet. Med. 31, 1631–1642 (2014)

Introduction In 2012, $471 bn was spent on diabetes treatment worldwide [1]. Although genetic predisposition contributes to the development of Type 2 diabetes [2], the Diabetes Prevention Program (DPP) and other randomized, controlled trials of lifestyle interventions among individuals with impaired glucose tolerance have proven to be both efficacious [3–6] and cost-effective [7] in preventing or delaying diabetes onset. Prospective observational studies have suggested that certain food groups and dietary patterns are associated with Correspondence to: Judith Wylie-Rosett. E-mail: [email protected]. (Clinical Trials Registry No: NCT00004992, NCT00038727)

ª 2014 The Authors. Diabetic Medicine ª 2014 Diabetes UK

incident Type 2 diabetes: meat and Western dietary patterns may increase risk, while whole grains, low-fat dairy products, Mediterranean dietary patterns and low-fat prudent dietary patterns may decrease risk [8–13]. Although some prevention trials have evaluated long-term adherence to specific dietary intervention goals, for example, decreasing the percentage of calories from total fat and increasing fibre density [6,14,15], to our knowledge, only one study has characterized long-term changes in food group intake [16]. There is also a dearth of scientific evidence relating to demographic predictors of long-term dietary modifications. Clinical trial data have linked self-reported Hispanic and black race/ethnicity to poorer dietary adherence [17]. Evaluating how race/ethnicity and other demographic factors are

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DIABETICMedicine

Long-term changes in dietary intake in the Diabetes Prevention Program Outcomes Study  L. M. Jaacks et al.

What’s new?  This is the first study to evaluate long-term changes in food group intake and food behaviours among a large, diverse sample of adults participating in a diabetes prevention trial in the USA.  Significant differences in nutrients and food behaviours were observed between the lifestyle arm and the metformin and placebo arms up to 9 years after randomization.  Key demographic groups at high risk of having poor dietary intake and dietary behaviours were identified and represent an important point for intervention. related to achieving dietary intervention goals may inform tailoring strategies, which is important for translating the DPP lifestyle intervention. The objectives of the present study were to compare change in dietary intake, with an emphasis on food groups and food behaviours, among treatment arms and to assess the differences in dietary intake among age, race/ethnicity and gender groups within treatment arms.

Subjects and methods

Outcomes Study (DPPOS), began in which all participants were offered lifestyle intervention sessions every 3 months [22]. Participants in the lifestyle intervention were also offered two four-session group classes per year during this time [22]. Of the 3234 randomized participants, a total of 2766 (86%; n = 910 lifestyle; n= 924 metformin, n = 932 placebo) were enrolled in the DPPOS. Study protocols were approved by the institutional review boards at all sites and written informed consent was obtained from all participants.

Dietary intake assessment

A modified version of the validated Insulin Resistance Atherosclerosis Study (IRAS) food frequency questionnaire was used to assess dietary intake in the DPP [23]. The 117-item questionnaire was administered by trained interviewers at baseline and at 1, 5, 6 and 9 years after randomization. Six food groups were developed based on the Food Guide Pyramid and 27 additional food groups were developed by the DPP Nutrition Coding Center [23]. A total of eight food groups were evaluated in the present analysis (Appendix S1). The nutrient content of foods was determined using the DietSys Nutrient Analysis Program and Nutrition Data System (version 2.6/8A/23, Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN, USA).

Sample population

The DPP was a multicentre, randomized, controlled trial that enrolled participants at high risk of developing Type 2 diabetes between 1996 and 1999 [18]. Recruitment goals included: ≥ 50% women, 20% >65 years old and 50% minority race/ethnicity [18]. A total of 3234 participants were randomized to intensive lifestyle intervention (n = 1079), 850 mg metformin twice daily (n = 1073) or placebo (n = 1082) [19]. The lifestyle intervention involved a 16-session core curriculum over the first 24 weeks, followed by an individualized counselling curriculum (at least monthly contact) with the primary intervention goals of achieving and maintaining a weight loss of ≥ 7% initial body weight and a moderate intensity activity level of ≥ 150 min per week [20]. Participants were advised to reduce dietary fat gram intake to < 25% of total calories based on a calorie estimate to achieve the weight loss goal, with the addition of a calorie goal if weight loss was not achieved after the first seven sessions [20]. Session materials and strategies to reduce fat and calorie intake were tailored to the needs of an ethnically diverse population. In July 2001, after the DPP results were released, participant intervention assignment was unmasked and all participants were offered a group-administered version of the 16-session lifestyle intervention curriculum [21]. Beginning in September 2002, a long-term follow-up study of participants in the DPP, the Diabetes Prevention Program

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Statistical analysis

Univariate statistics, including medians, 25th and 75th percentiles and percentages (n), are presented for dietary variables over time. Because of space limitations and the similarity between years 5 and 6, we choose to present data from baseline and 1, 5 and 9 years after randomization; however, all statistical tests and models included year 6 data. Repeated measures ANOVA with generalized estimating equations was used to assess changes in nutrients and food groups among treatment arms and demographic strata over time [24]. Proportional odds modelling with generalized estimating equations was used to model food behaviour variables over time [25]. Because of the treatment and time interaction, we assessed demographic differences in nutrient intake stratified by treatment group. As a result of the intensive lifestyle intervention in the first year of the DPP, the effect of time was not linear and time was therefore included in the models as a categorical variable. Baseline nutrient intake was adjusted in all models. As a sensitivity analysis to explore the independence of demographic effects, multivariate models including age, race/ethnicity and gender were evaluated. A P value < 0.05 was considered to indicate statistical significance. All analyses were conducted using SAS software (version 9.3, Cary, NC, USA).

ª 2014 The Authors. Diabetic Medicine ª 2014 Diabetes UK

Research article

Results Nine years after randomization, 74% of the original participants in the lifestyle arm and 77% of the original participants in the metformin and placebo arms had dietary data. Detailed participant demographic information has been published elsewhere [5]. There were no differences in age, gender or race/ethnicity among treatment arms at any time point. Because age has been reported in previous DPP/DPPOS analyses as a key predictor of achieving intervention goals [26,27], we chose to present results stratified by age (Tables 1–3). Key differences across racial/ethnic groups and gender are described in the text and presented in Figs 1 and 2. Results were consistent in sensitivity analyses of multivariate models including all demographic variables, therefore, parsimonious models with only the demographic variable of interest are presented.

Effect of treatment arm on dietary intake and food behaviours over time

Participants in the lifestyle arm maintained a lower percentage of calories from total fat and saturated fat and a higher fibre intake compared with those in the metformin and placebo arms up to 9 years after randomization (Table 1). At 1 year after randomization, participants in the lifestyle arm had significantly higher fruit and vegetable intake, and lower red meat, dairy and sweet intakes compared with the participants in the metformin and placebo arms. By 5 years after randomization, the observed difference in fruit intake was only marginally significant (P = 0.07), and although the lower red meat and sweet intakes remained statistically significant, the difference was small, only 0.1 servings/day. Overall P values comparing 9-year averages were significant for fruit, vegetables, poultry, red meat and sweets (Table 2). Participants in the lifestyle arm were more likely to report using low-fat foods ‘often/always’ at every time point, although the proportion decreased over time (Table 3). They were also more likely to report using fat/oil in cooking less than once per week up to 5 years after randomization. Effect of age on dietary intake and food behaviours over time

Compared with younger participants (aged 25–44 years), older participants (aged ≥ 60 years) had a lower percentage of calories from total fat and saturated fat and a higher fibre intake in all treatment arms (Table 1). Older participants had higher fruit and lower poultry intakes compared with younger participants in all treatment arms (Table 2). In the lifestyle arm, older participants also had higher vegetable intakes compared with younger participants. In the metformin arm, older participants had lower red meat and dairy intakes. ª 2014 The Authors. Diabetic Medicine ª 2014 Diabetes UK

DIABETICMedicine

Older participants were more likely to report drinking alcohol at least once per week compared with younger participants in all treatment arms (Table 3). In the placebo arm, older participants were also more likely to report using fat/oil in cooking less than once per week compared with younger participants.

Effect of race/ethnicity on dietary intake and food behaviours over time

In all treatment arms, on average across the 9 years of observation, white and black participants had a higher percentage of calories from fat compared with Hispanic (all P < 0.05) and Asian participants (P = 0.07 for comparisons in the lifestyle arm; P < 0.05 in the metformin and placebo arms; Fig. 1a). American Indian participants had the highest percentage of calories from fat of all the racial/ethnic groups; differences were significant compared with Hispanic (P < 0.001) and Asian participants (P = 0.006) and the difference approached significance when compared with white (P = 0.06) and black (P = 0.11) participants. Hispanic participants tended to have higher fibre intakes compared with white participants in all treatment arms (all P < 0.05) and also compared with black (P < 0.001) and American Indian participants (P = 0.007) in the placebo arm and American Indian participants in the lifestyle arm (P < 0.001; Fig. 1b). No consistent differences in fruit intake across racial/ ethnic groups were observed in any of the treatment arms, although white and American Indian participants tended to have lower fruit intakes compared with Hispanic participants in the lifestyle arm (P = 0.05 and P = 0.006, respectively; Fig. 1c). Additional analysis of a food group including only fruit juice indicated that black participants had significantly higher fruit juice intakes compared with all other racial/ethnic groups in the lifestyle arm and compared with all other racial/ethnic groups except for American Indians in the metformin and placebo arms (P = 0.05 and P = 0.50 comparing black and American Indian participants in the metformin and placebo arms, respectively). The 9-year average intake for black participants in the lifestyle arm was 0.67 servings/day compared with, for example, 0.51 servings/day for white participants (P < 0.001) and 0.53 servings/day for Hispanic participants (P = 0.009). In the lifestyle arm, white participants had higher red meat intakes compared with black (P = 0.0002), Hispanic (P = 0.01) and Asian participants (P = 0.0003), but there was no significant difference compared with American Indian participants (P = 0.80; Fig. 1d). American Indian participants had significantly higher red meat intake compared with all other racial/ethnic groups in the placebo arm and compared with black participants (P = 0.02) and Asian participants (P = 0.005) in the lifestyle arm. Asian and American Indian participants had lower vegetable intakes compared with white (P = 0.03 and P = 0.006, respectively)

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1634 1560 (1223–2027)† 1640 (1271–2199) 1578 (1238–2007) 1494 (1171–1905) 35.3 (29.7–40.2)† 37.5 (32.1–41.6)* 35.1 (29.7–40.4) 33.0 (27.6–38.0) 12.1 (10.4–14.9)† 12.8 (10.4–14.9)* 12.1 (9.9–14.3)* 11.0 (8.9–13.3) 46.6 (40.8–52.6)† 44.2 (39.2–50.0)* 46.6 (41.3–52.5) 49.3 (44.2–55.2) 9.0 (7.1–11.2)† 7.3 (5.7–8.6)* 8.6 (6.9–10.7)* 9.7 (7.8–12.1)

1565 (1210–2039) 1594 (1262–2187) 1573 (1243–2011) 1450 (1140–1901) 32.9 (28.3–38.6) 35.2 (29.5–39.8) 32.7 (28.1–38.1) 31.3 (26.7–36.0) 11.2 (9.1–13.6) 11.9 (9.8–14.4) 11.0 (8.9–13.4) 10.2 (8.3–13.0) 48.9 (43.2–54.6) 46.5 (41.5–52.2) 48.6 (43.3–54.7) 51.8 (45.9–56.2) 9.0 (7.3–11.7) 8.1 (5.9–10.0) 8.5 (7.1–10.8) 10.3 (8.4–12.9)

1713 (1307–2213) 1841 (1363–2338) 1713 (1305–2189) 1602 (1268–2062) 33.3 (29.1–37.7) 34.5 (30.8–38.5) 33.2 (28.6–37.6) 31.9 (27.2–36.4) 11.2 (9.3–13.0) 11.9 (10.3–13.7) 11.0 (9.0–13.0) 10.5 (8.5–12.1) 49.0 (44.2–54.0) 47.8 (43.4–52.8) 49.0 (44.5–53.9) 51.2 (45.3–56.8) 8.1 (6.4–10.3) 7.1 (6.0–9.0) 8.2 (6.5–10.2) 9.0 (7.2–11.4)

1915 (1475–2607) 2091 (1615–2892) 1921 (1468–2582) 1692 (1380–2255) 34.4 (29.1–39.1) 35.7 (31.1–40.4) 34.5 (29.1–38.9) 31.6 (26.5–37.5) 11.6 (9.4–13.5) 12.3 (10.4–14.2) 11.5 (9.3–13.4) 10.5 (8.1–12.6) 48.2 (43.1–54.0) 47.1 (42.1–52.1) 48.0 (43.0– 53.6) 50.7 (45.6–57.5) 7.4 (6.0–9.4) 6.6 (5.4–8.2) 7.6 (6.1–9.7) 8.6 (6.8–10.7)

Year 1

8.4 (6.7–10.8) 6.7 (5.6–9.4) 8.0 (6.6–10.1) 9.6 (7.4–12.3)

46.7 (41.4–52.1) 45.5 (40.1–49.8) 46.5 (41.5–52.0) 51.0 (43.8–55.5)

12.2 (10.3–14.2) 12.9 (11.2–14.7) 12.2 (10.1–14.2) 11.3 (9.7–13.1)

35.2 (30.9–40.8) 36.9 (33.3–42.0) 35.2 (30.9–41.0) 33.1 (29.3–38.7)

1664 (1294–2144) 1859 (1412–2424) 1629 (1273–2091) 1547 (1258–2019)

Year 5

8.4 (6.7–10.7)† 6.7 (5.6–9.1)* 8.0 (6.4–10.0)* 8.9 (7.4–11.2)

45.2 (40.1–50.4)† 42.7 (37.9–47.7)* 45.0 (39.9–50.5)* 47.8 (43.8–53.1)

13.1 (10.9–15.1)† 13.8 (11.8–15.9)* 13.0 (10.7–15.0)* 12.2 (10.2–14.0)

37.2 (32.4–41.8)† 39.1 (34.6–43.9)* 36.9 (32.2–41.6)* 34.7 (31.2–39.7)

1641 (1262–2115)† 1759 (1375–2242) 1670 (1284–2115) 1454 (1156–1871)

Year 9

7.6 (6.0–9.6) 6.8 (5.5–8.5) 7.6 (6.0–9.5) 9.0 (7.1–11.4)

48.3 (43.4–54.2) 47.0 (42.4–52.3) 48.7 (43.6–54.1) 50.0 (45.2–56.5)

11.4 (9.2–13.7) 12.2 (9.9–14.1) 11.4 (9.4–13.6) 10.0 (8.2–12.3)

34.1 (29.2–38.9) 35.6 (30.4–39.8) 34.2 (29.3–38.7) 31.3 (26.9–37.1)

1889 (1426–2506) 1977 (1469–2666) 1920 (1473–2526) 1666 (1328–2191)

Baseline

Placebo

8.2 (6.5–10.3) 7.3 (6.1–9.4) 8.3 (6.6–10.2) 9.2 (7.5–11.5)

49.0 (43.8–54.0) 47.1 (42.4–52.3) 49.3 (44.4–54.1) 50.5 (46.4–55.6)

11.0 (8.9–13.1) 11.9 (9.9–13.7) 11.0 (8.9–13.0) 9.8 (7.8–12.1)

33.3 (28.9–37.5) 34.5 (30.4–38.7) 33.0 (29.0–37.4) 31.2 (26.3–35.7)

1702 (1298–2255) 1711 (1357–2367) 1734 (1278–2293) 1611 (1273–2095)

Year 1

8.3 (6.5–10.8) 7.1 (6.0–9.2) 7.8 (6.4–10.0) 9.7 (7.8–12.0)

45.9 (40.5–51.6) 43.5 (38.5–49.2) 46.1 (40.9–51.2) 49.7 (43.7–54.7)

12.3 (10.1–14.6) 13.5 (11.2–15.5) 12.4 (10.3–14.4) 11.0 (8.8–13.4)

36.0 (30.8–41.1) 38.4 (33.6–43.5) 36.0 (31.0–40.9) 32.7 (27.9–37.8)

1617 (1255–2171) 1656 (1259–2220) 1659 (1288–2249) 1496.5 (1129–1873)

Year 5

8.5 (6.7–10.5)† 6.8 (5.7–9.7)* 7.9 (6.5–9.9)* 9.3 (7.3–11.5)

44.7 (39.2–49.7)† 42.4 (37.1–47.7)* 44.9 (40.0–49.8)* 47.3 (42.1–52.4)

13.1 (10.8–15.2)† 14.0 (11.7–15.9)* 12.8 (10.7–15.2)* 12.2 (9.9–14.4)

37.3 (32.5–42.4)† 38.8 (34.1–44.1)* 37.2 (32.8–42.1)* 35.0 (30.3–39.3)

1613 (1227–2090)† 1623.2 (1225–2161) 1663 (1269–2173) 1501 (1128–1868)

Year 9

Values are reported as medians (25th–75th percentiles). † Overall P < 0.05 from repeated measures ANOVA with generalized estimating equation assessing changes in nutrient intake across treatment arms over time, adjusted for baseline nutrient intake. *Overall P < 0.05 from pairwise comparison (≥ 60 years old as referent) for repeated measures ANOVA with generalized estimating equation assessing changes in nutrient intake across age strata over time, adjusted for baseline nutrient intake.

Total calories All 1876 1521 (1452–2550) (1192–1986) 25–44 2059 1580 years (1533–2859) (1228–2090) 45–59 1881 1514 years (1442–2511) (1192–1971) ≥60 1758 1468 years (1340–2195) (1101–1870) Percent of calories from fat All 34.4 27.1 (29.6–38.5) (23.0–31.5) 25–44 35.6 28.5 years (31.3–39.8) (24.4–33.0) 45–59 34.4 26.8 years (29.7–38.5) (22.8–31.0) ≥60 32.6 25.7 years (26.9–36.6) (21.7–29.6) Percent of calories from saturated fat All 11.6 8.5 (9.3–13.6) (6.9–10.5) 25–44 12.3 9.4 years (10.4–14.0) (7.5–11.4) 45–59 11.5 8.4 years (9.1–13.6) (6.9–10.1) ≥60 10.4 7.7 years (8.4–12.7) (6.3–9.6) Percent of calories from carbohydrates All 48.6 54.4 (43.6–54.1) (49.2–60.0) 25–44 47.5 52.3 years (42.1–51.9) (47.7–58.1) 45–59 48.8 54.7 years (43.4–54.2) (49.3–60.3) ≥60 51.4 56.2 years (46.3–57.2) (51.6–61.0) Dietary fiber (g/1000 kcal) All 7.7 10.0 (6.0–9.8) (8.0–12.3) 25–44 6.8 8.9 years (5.5–8.5) (6.9–11.0) 45–59 7.7 10.0 years (6.2–9.9) (8.3–12.2) ≥60 8.9 11.4 years (7.0–11.6) (9.4–13.5)

Year 9

Baseline

Year 5

Baseline

Year 1

Metformin

Lifestyle

Table 1 Nutrient intake for participants in the lifestyle, metformin and placebo arms, according to age group

DIABETICMedicine Long-term changes in dietary intake in the Diabetes Prevention Program Outcomes Study  L. M. Jaacks et al.

ª 2014 The Authors. Diabetic Medicine ª 2014 Diabetes UK

ª 2014 The Authors. Diabetic Medicine ª 2014 Diabetes UK

(2.3–4.7) (2.4–5.2) (2.4–4.7) (2.1–4.0)

(1.3–3.8) (1.0–3.5) (1.3–3.9) (2.0–4.4)

(1.8–3.6) (1.8–3.4) (1.8–3.8) (1.8–3.5)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.4)

(0.3–0.8) (0.3–0.9) (0.3–0.8) (0.2–0.6)

(0.4–1.2) (0.4–1.5) (0.4–1.1) (0.3–0.9)

(0.6–2.1) (0.7–2.3) (0.6–2.0) (0.5–1.9)

(0.5–2.0) (0.6–2.5) (0.5–2.0) (0.5–1.7)

3.3 3.4 3.4 2.8

2.5 2.0 2.5 2.7

2.5 2.5 2.6 2.5

0.2 0.2 0.2 0.2

0.5 0.6 0.5 0.4

0.7 0.8 0.6 0.5

1.2 1.3 1.1 1.1

1.1 1.2 1.0 1.0

0.6 0.6 0.6 0.6

0.9 1.1 0.9 0.8

0.4 0.5 0.4 0.3

0.5 0.6 0.5 0.4

0.2 0.2 0.2 0.2

2.8 2.6 2.8 3.0

2.8 2.4 2.9 3.4

2.9 3.2 3.1 2.9

(0.3–1.1) (0.3–1.3) (0.2–1.0) (0.3–1.0)

(0.5–1.6) (0.6–1.6) (0.5–1.6) (0.5–1.5)

(0.2–0.8) (0.3–0.8) (0.2–0.7) (0.2–0.7)

(0.3–0.8) (0.3–0.9) (0.3–0.8) (0.2–0.6)

(0.1–0.4) (0.1–0.3) (0.1–0.4) (0.1–0.4)

(1.8–3.9) (1.8–3.7) (1.8–4.0) (2.1–4.0)

(1.6–4.0) (1.3–3.5) (1.7–3.9) (2.2–4.7)

(2.1–4.0) (2.3–4.5) (2.2–4.2) (2.0–3.9)

0.6 0.6 0.6 0.5

1.3 1.4 1.3 1.1

0.6 0.8 0.6 0.5

0.5 0.5 0.5 0.4

0.2 0.2 0.2 0.2

2.6 2.6 2.6 2.8

2.5 2.1 2.6 3.1

2.7 2.9 2.7 2.7

(0.2–1.1) (0.2–1.1) (0.2–1.2) (0.3–1.0)

(0.7–2.2) (0.8–2.3) (0.7–2.2) (0.7–2.0)

(0.3–1.1) (0.4–1.3) (0.3–1.1) (0.2–0.8)

(0.3–0.8) (0.3–0.8) (0.3–0.8) (0.2–0.6)

(0.1–0.4) (0.1–0.4) (0.1–0.5) (0.1–0.4)

(1.7–3.8) (1.6–3.6) (1.7–3.9) (1.8–4.0)

(1.4–3.8) (1.1–3.2) (1.5–3.9) (2.2–4.5)

(1.9–4.1) (2.0–4.4) (1.9–4.0) (1.8–3.9)

0.5 0.6 0.5 0.6

1.4 1.5 1.4 1.3

0.7 0.8 0.6 0.5

0.5 0.5 0.5 0.4

0.2 0.2 0.3 0.2

2.6 2.5 2.6 2.8

2.4 1.8 2.4 3.1

2.6 2.6 2.7 2.5

1.3 1.5 1.2 1.1 1.1 1.3 1.1 1.0

(0.2–1.0)† (0.3–1.1) (0.2–0.9) (0.3–1.2)

0.7 0.8 0.7 0.6

(0.3–1.1)† (0.4–1.3) (0.3–1.1) (0.3–0.9) (0.8–2.2) (0.9–2.5) (0.8–2.1)* (0.8–2.1)

0.5 0.6 0.5 0.3

(0.3–0.8)† (0.3–0.9)* (0.3–0.8)* (0.2–0.7)

2.6 2.4 2.8 2.5

(1.8–3.7)† (1.6–3.4)* (1.9–3.8)* (1.8–3.9) 0.2 0.2 0.2 0.2

2.4 2.0 2.5 2.7

(1.4–3.7)† (1.0–3.2)* (1.4–3.5)* (1.9–4.2)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.4)

3.4 3.8 3.4 3.2

(1.9–3.7) (1.9–3.8) (1.8–3.7) (1.8–3.6)

(0.6–1.9) (0.6–2.3) (0.5–1.9) (0.5–1.6)

(0.7–2.2) (0.8–2.5) (0.6–2.0) (0.6–2.0)

(0.4–1.2) (0.4–1.3) (0.4–1.2) (0.2–0.9)

(0.3–0.8) (0.3–0.9) (0.3–0.8) (0.1–0.6)

(0.1–0.4) (0.1–0.3) (0.1–0.4) (0.1–0.3)

(1.7–3.7) (1.6–3.7) (1.9–3.7) (1.7–3.8)

(1.3–3.7) (1.0–3.5) (1.4–3.6) (1.5–4.4)

(2.4–4.9) (2.8–5.5) (2.4–4.8) (2.1–4.2)

0.8 0.9 0.8 0.8

1.2 1.4 1.1 1.0

0.6 0.7 0.6 0.6

0.5 0.5 0.5 0.4

0.2 0.2 0.2 0.2

2.5 2.5 2.6 2.5

2.4 2.0 2.5 2.7

3.1 3.2 3.1 2.9

(0.4–1.4) (0.5–1.6) (0.4–1.4) (0.4–1.2)

(0.6–2.0) (0.7–2.1) (0.6–2.0) (0.5–1.8)

(0.3–1.0) (0.4–1.2) (0.3–1.0) (0.3–0.9)

(0.3–0.7) (0.3–0.8) (0.3–0.8) (0.2–0.5)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.3)

(1.8–3.6) (1.6–3.6) (1.8–3.6) (1.9–3.7)

(1.4–3.8) (1.1–3.4) (1.5–3.8) (1.9–3.9)

(2.2–4.2) (2.3–4.5) (2.2–4.2) (2.0–3.9)

Year 1

0.7 0.8 0.6 0.6

1.3 1.5 1.3 1.2

0.7 1.0 0.7 0.6

0.5 0.5 0.5 0.3

0.2 0.2 0.2 0.2

2.6 2.5 2.8 2.5

2.4 1.8 2.5 2.7

2.9 3.2 2.7 2.8

(0.3–1.3) (0.4–1.5) (0.3–1.2) (0.3–1.1)

(0.8–2.2) (0.9–2.5) (0.7–2.1) (0.7–2.0)

(0.4–1.2) (0.5–1.6) (0.4–1.2) (0.3–1.0)

(0.3–0.7) (0.3–0.8) (0.3–0.8) (0.2–0.5)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.4)

(1.8–3.6) (1.8–3.4) (1.8–3.8) (1.9–3.5)

(1.4–3.8) (1.2–3.3) (1.4–3.8) (1.8–4.1)

(2.0–4.0) (2.2–4.4) (1.9–4.0) (2.0–3.7)

Year 5

0.6 0.6 0.6 0.6

1.4 1.5 1.4 1.1

0.7 0.9 0.7 0.6

0.5 0.6 0.5 0.3

0.2 0.2 0.3 0.2

2.6 2.5 2.6 2.6

2.2 1.6 2.4 2.6

2.7 2.8 2.7 2.4

(0.3–1.1)† (0.3–1.1)* (0.3–1.1) (0.3-1.0)

(0.7–2.3) (0.8–2.4)* (0.8–2.4) (0.7–1.9)

(0.4–1.2)† (0.5–1.4)* (0.4–1.2)* (0.3–0.9)

(0.2–0.7)† (0.3–0.8)* (0.3–0.7)* (0.1–0.5)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.4)

(1.7–3.6)† (1.6–3.7) (1.8–3.7) (1.7–3.4)

(1.3–3.5)† (1.0–2.9)* (1.4–3.6) (1.7–4.1)

(1.9–3.6) (1.9–3.9) (1.9–3.7) (1.8–3.3)

Year 9

1.0 1.2 1.0 0.7

1.3 1.3 1.3 1.2

0.6 0.7 0.6 0.5

(0.5–1.8) (0.6–2.0) (0.5–2.0) (0.4-1.4)

(0.7–2.1) (0.8–2.4) (0.6–2.1) (0.5–1.8)

(0.3–1.1) (0.3–1.2) (0.3–1.1) (0.2–0.9)

(0.3–0.8) (0.3–0.9) (0.3–0.8) (0.2–0.6)

(0.1–0.4) (0.1–0.3) (0.1–0.4) (0.1–0.4)

0.2 0.2 0.2 0.2 0.5 0.5 0.5 0.4

(1.7–3.7) (1.7–3.5) (1.7–3.7) (1.7–3.8)

(1.2–3.9) (1.0–3.3) (1.3–4.0) (1.6–4.3)

(2.3–4.8) (2.5–5.0) (2.3–4.8) (2.1–4.3)

2.6 2.5 2.7 2.6

2.4 1.9 2.4 2.8

3.4 3.6 3.5 3.1

Baseline

Placebo

(0.4–1.4) (0.4–1.5) (0.4–1.3) (0.3–1.0)

(0.6–1.9) (0.7–2.0) (0.6–1.9) (0.6–1.8)

1.1 1.2 1.0 1.1 0.7 0.9 0.7 0.6

(0.3–1.0) (0.4–1.2) (0.3–1.0) (0.3–0.9)

(0.3–0.8) (0.3–0.8) (0.3–0.8) (0.2–0.6)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.4)

(1.8–3.8) (1.8–3.7) (1.8–3.8) (1.8–3.7)

(1.4–3.8) (1.0–3.2) (1.5–3.9) (1.7–4.4)

(2.1–4.2) (2.2–4.4) (2.1–4.1) (2.2–4.2)

0.6 0.6 0.6 0.5

0.5 0.5 0.5 0.4

0.2 0.2 0.2 0.2

2.6 2.5 2.6 2.7

2.3 2.0 2.4 2.8

3.0 3.2 3.0 3.1

Year 1

0.7 0.7 0.7 0.6

1.3 1.4 1.3 1.3

0.7 0.8 0.8 0.6

0.5 0.5 0.5 0.4

0.2 0.2 0.3 0.2

2.5 2.4 2.6 2.6

2.3 1.7 2.4 2.6

2.8 2.9 2.9 2.6

(0.3–1.2) (0.3–1.4) (0.3–1.3) (0.2–1.0)

(0.7–2.1) (0.8–2.2) (0.7–2.2) (0.6–1.9)

(0.4–1.2) (0.4–1.4) (0.4–1.3) (0.3–1.0)

(0.3–0.8) (0.3–0.8) (0.3–0.8) (0.2–0.6)

(0.1–0.4) (0.1–0.4) (0.1–0.4) (0.1–0.5)

(1.7–3.7) (1.7–3.4) (1.7–3.8) (1.9–3.5)

(1.2–3.5) (0.9–2.8) (1.3–3.7) (1.8–4.1)

(1.9–4.0) (2.0–4.0) (1.9–4.1) (1.9–3.9)

Year 5

0.6 0.6 0.6 0.5

1.4 1.4 1.4 1.3

0.7 0.9 0.7 0.6

0.5 0.5 0.5 0.3

0.2 0.2 0.2 0.2

2.5 2.4 2.6 2.4

2.2 1.8 2.4 2.6

2.7 2.8 2.7 2.4

(0.3–1.1)† (0.3–1.1)* (0.3–1.1) (0.2–0.9)

(0.8–2.4) (1.0–2.3) (0.8–2.5) (0.9–2.2)

(0.4–1.2)† (0.5–1.4) (0.4–1.2) (0.3–1.0)

(0.3–0.7)† (0.3–0.8)* (0.3–0.7)* (0.1–0.5)

(0.1–0.4) (0.1–0.3) (0.1–0.4) (0.1–0.4)

(1.7–3.5)† (1.6–3.5) (1.7–3.6) (1.8–3.6)

(1.3–3.4)† (1.0–2.8)* (1.4–3.4) (1.6–3.6)

(1.7–3.8) (1.8–4.0) (1.8–3.9) (1.7–3.3)

Year 9

Values reported as medians (25th–75th percentiles). † Overall P < 0.05 from repeated measures analysis of variance with generalized estimating equation assessing changes in food group intake across treatment arms over time, adjusted for baseline food group intake. *Overall P < 0.05 from pairwise comparison (≥ 60 years old as referent) for repeated measures analysis of variance with generalized estimating equation assessing changes in food group intake across age strata over time, adjusted for baseline food group intake.

Grains All 25–44 years 45–59 years ≥60 years Fruits All 25–44 years 45–59 years ≥60 years Vegetables All 25–44 years 45–59 years ≥60 years Fish All 25–44 years 45–59 years ≥60 years Poultry All 25–44 years 45–59 years ≥60 years Red meat All 25–44 years 45–59 years ≥60 years Dairy All 25–44 years 45–59 years ≥60 years Sweets All 25–44 years 45–59 years ≥60 years

Year 9

Baseline

Year 5

Baseline

Year 1

Metformin

Lifestyle

Table 2 Food group intake (servings/day) for participants in the lifestyle, metformin and placebo arms over time according to age group

Research article DIABETICMedicine

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Long-term changes in dietary and food intake behaviour in the Diabetes Prevention Program Outcomes Study.

To compare change in dietary intake, with an emphasis on food groups and food intake behaviour, over time across treatment arms in a diabetes preventi...
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