Effects of Reduced-fat Diets Consumed Ad Libitum on Intake of Nutrients, Particularly Antioxidant Vitamins

https://doi.org/10.1016/S0002-8223(99)00339-9Get rights and content

Abstract

Objectives To determine whether a reduced-fat diet consumed ad libitum can achieve the recommended intakes of other macronutrients, fiber, and cholesterol and whether such a diet affects intake of other important micronutrients such as fat-soluble vitamins.

Design Twelve-month, randomized, controlled trial of a reduced-fat, ad libitum diet vs usual diet.

Subjects One hundred ten adults older than 40 years with glucose intolerance (2-hour blood glucose concentration=7.0 to 11.0 mmol/L) who were selected from a previous workforce survey.

Intervention Monthly small-group meetings aimed at identifying sources of dietary fat and ways to reduce fat consumption.

Main outcome measures Nutrient intakes derived from 3-day food diaries at the beginning and end of the study. Blood levels of retinol, α-tocopherol, and beta carotene at the end of the study.

Statistical analyses performed Unpaired t tests for determining changes in nutrient intake and antioxidant vitamin concentrations. Separate analyses were conducted with users of mineral and vitamin supplements and people who changed smoking status to reduce potential confounding.

Results Fat intake decreased from 35% to 26% of energy in the reduced-fat diet group compared with a 2% decrease in the control group (P<.0001). Total energy intake also decreased in the 2 groups (−362 vs −59 kcal/day, P<.02). Those changes were reflected in a 3.1±4.7 kg (mean± standard deviation) weight loss in the intervention group compared with a 0.4±3.0 kg weight gain in the control group (P<.0001). There were no differences between groups in the changes in micronutrient intakes, except for an energy-adjusted increase in beta carotene intake in the reduced-fat diet group. Serum retinol and α-tocopherol concentrations were not different between the groups, but the reduced-fat diet group had higher beta carotene concentrations (P=.009).

Applications A reduced-fat, ad libitum diet can be prescribed to improve overall macronutrient intake and achieve modest weight loss without sacrificing micronutrient intakes. J Am Diet Assoc. 1999;99:1400–1405.

Section snippets

Subjects

Participants were selected from the Workforce Diabetes Survey (19) in which glucose tolerance tests were performed in 5,677 workers older than 40 years from 41 worksites around Auckland, New Zealand, between 1988 and 1990. One hundred sixty-two (2.8%) of those surveyed were classified as having impaired glucose tolerance (2-hour blood glucose concentration 7.8 to 11.0 mmol/L)1

Subjects

Sixty-three percent of participants who started the trial completed it with full dietary data available for analysis (N=110; see Table 1). The mean age for this group was 53 years; the range was narrow because the minimum age for inclusion in the original workforce diabetes survey was 40 years. No differences were noted in mean initial weight or body mass index (calculated as kg/m2) between the 2 groups (reduced-fat intake and control). All participants originally had a 2-hour blood glucose

Discussion

We examined the effects of a 12-month, reduced-fat diet consumed ad libitum on dietary intake of macronutrients and micronutrients and on serum levels of antioxidants. Total fat and saturated fat intake decreased significantly, as did their contribution to total energy in the reduced-fat group. Absolute intake of carbohydrate did not change, which indicates no compensatory response for the decrease in energy from fat. Intake of micronutrients was not compromised by the reduction in fat intake

Applications/Conclusions

■ A dietary approach to weight loss that focuses on the reduction of total fat within an otherwise ad libitum diet achieves recommended intakes of macronutrients and dietary cholesterol. To increase intake of dietary fiber, people require more specific instructions such as choosing fiber-rich breads and cereals and increasing vegetable consumption.

■ Similarly, people at high risk of cardiovascular disease may require specific advice on increasing vegetable oil consumption. A deduction in

References (35)

Cited by (0)

View full text