A clinical trial to selectively change dietary fat and/or energy intake in women: the Women's Diet Study

Applying Psychological Theories to Promote Long-Term Maintenance of Health Behaviors

Behavioral health theory provides a framework for researchers to design, implement, and evaluate the effects of health promotion programs. However, limited research has examined theories used in interventions to promote long-term maintenance of health behaviors. The purpose of this review was to evaluate the available literature and identify prominent behavioral health theories used in intervention research to promote maintenance of health behaviors. We reviewed theories used in intervention research assessing long-term maintenance (≥ 6 months post-intervention) of physical activity, weight loss, and smoking cessation. Five prominent behavioral theories were referenced by the 34 studies included in the review: Self-Determination Theory, Theory of Planned Behavior, Social Cognitive Theory, Transtheoretical Model, and Social Ecological Model. Descriptions and examples of applications of these theories are provided. Implications for future research are discussed.

Clinical trial: Efficacy of a low or modified fat diet for the prevention of gastrointestinal toxicity in patients receiving radiotherapy treatment for pelvic malignancies

BACKGROUND

Inflammatory responses to pelvic radiotherapy can result in severe changes to normal gastrointestinal function with potentially severe long-term effects. Reduced or modified fat diets may confer benefit.

METHODS

This randomised controlled trial recruited patients with gynaecological, urological or lower gastrointestinal malignancy due to receive radical radiotherapy. Patients were randomised to a low fat (20% total energy from long chain triglycerides), modified fat (20% from long chain triglycerides and 20% from medium chain triglycerides) or normal fat diet (40% total energy from long chain triglycerides). The primary outcome was a difference in change in Inflammatory Bowel Disease Questionnaire--Bowel (IBDQ-B) score, from the start to end of radiotherapy.

RESULTS

A total of 117 patients with pelvic tumours (48% urological; 32% gastrointestinal; 20% gynaecological), with mean (SD) age: 65 (11.0) years, male:female ratio: 79:38, were randomised. The mean (SE) fall in paired IBDQ-B score was -7.3 (0.9) points, indicating a worsening toxicity. Differences between groups were not significant: P = 0.914 (low versus modified fat), P = 0.793 (low versus normal fat) and P = 0.890 (modified versus normal fat). The difference in fat intake between low and normal fat groups was 29.5 g [1109 kJ (265 kcal)] amounting to 11% (of total energy intake) compared to the planned 20% differential. Full compliance with fat prescription was only 9% in the normal fat group compared to 93% in the low fat group.

CONCLUSIONS

A low or modified fat diet during pelvic radiotherapy did not improve gastrointestinal symptom scores compared to a normal fat intake. An inadequate differential in fat intake between the groups may have confounded the results.

Levels of 5-hydroxymethyl-2′-deoxyuridine in DNA from women participating in an intervention trial of low-fat and low-energy diets

Oxidative DNA damage in blood appears to be useful as a marker of systemic oxidative stress levels. Dietary factors such as fat and energy intakes have been indicated to affect oxidative stress levels, and this may be an important mechanism by which diet can modulate cancer risk. The primary objective of this study was to investigate the effects of dietary intervention in premenopausal women on the levels of one type of oxidative DNA damage: 5-hydroxymethyl-2'-deoxyuridine. The trial randomly assigned women to control, low-fat, low-energy or combination low-fat/low-energy diets for 12 weeks. Blood samples were obtained every 2 weeks, and DNA was analysed for the levels of 5-hydroxymethyl-2'-deoxyuridine. Levels of DNA damage declined with time in each diet arm, including the control arm. The decreases were greater in the two arms with low-energy intake, but not significantly so. The numbers of women who exhibited decreased 5-hydroxymethyl-2'-deoxyuridine levels at 12 weeks versus baseline levels, however, was significantly greater in women assigned to any intervention diet (79%) than in the control arm (50%). Low-fat and low-energy diets therefore had a small effect on changes in oxidative DNA damage levels. The women participating in this study were not selected on the basis of increased cancer risk; therefore, they may have had low baseline levels of damage that were not amenable to further reduction by dietary change.

A dietary intervention to elicit rapid and complex dietary changes for studies investigating the effects of diet on tissues collected during invasive surgical procedures

Nutrition intervention trials in patients undergoing surgical treatment for cancer offer a unique opportunity to study the mechanisms and pathways that underlie diet and cancer associations in target tissues. However, due to the short time period between diagnosis and treatment, traditional dietary intervention methods are not feasible. This report describes a novel dietary intervention program designed to elicit rapid and complex dietary change during a condensed study period. The intervention, based on Consumer Information Processing, used standardized menus and exchange lists to guide food choices, and was delivered using a single, in-person session followed by telephone-based counseling. This intervention program was used in a small pilot study evaluating the short-term effects of dietary change in men with newly diagnosed prostate cancer. Eight men were randomly assigned to either a low-fat/low-glycemic load or standard American diet during the 4 weeks preceding prostate surgery. Participants completed 24-hour dietary recalls each week, and were weighed at baseline and at surgery. Compared to men in the standard American arm (n=4), men in the low-fat/low-glycemic arm (n=4) reported consuming less total fat (51.0+/-36.0 vs 93.5+/-8.4 g/day, P=0.06), and had a lower glycemic load (134.8+/-6.0 vs 266.3+/-36.8 units/day, P<0.001). Men in the low-fat/low-glycemic arm lost a mean of 5.3+/-1.7 kg and men in the standard American arm gained 0.8+/-4.5 kg (P=0.04). Results of this small pilot study suggest that a relatively simple and minimally burdensome dietary intervention can elicit rapid and complex dietary changes that are maintained over a 4-week study period. Further studies in larger and more diverse populations are needed to fully understand the potential of this novel intervention approach.

Design of a Mediterranean exchange list diet implemented by telephone counseling

A Greek-Mediterranean dietary pattern has two distinct aspects that differ relative to average intakes in the United States: a high intake of monounsaturated fats and a high intake of fruit and vegetables. The purpose of the study was to develop and test an exchange list Greek-Mediterranean diet that could be used in future clinical trials of breast cancer prevention. A total of 69 women, ages 25 to 59 years, were randomized to either continue their own usual diet or follow an intervention diet for 6 months during 2004 through 2005. Intervention goals were to decrease usual fat intakes by about half and to replace those fats with olive oil and other high-monounsaturated fatty acid foods; increase fruit and vegetable intakes to 7 to 9 servings/day, depending on energy intake; and consume at least one serving per day each of culinary herbs and allium vegetables. Registered dietitians provided exchange goals and individualized telephone counseling, and diets were self-selected using a Mediterranean exchange list developed specifically for this study. Changes in diet were assessed by 7-day food records. Results demonstrated that counseling using the Mediterranean exchange list was effective for large dietary changes relative to the nonintervention group. Repeated measures analysis of variance indicated a statistically significant 48% increase in dietary monounsaturated fat with no appreciable change in total fat intake, and a significant increase in fruit and vegetable intake from 4.0 to 8.6 servings/day (P < 0.05).

A meta-analysis of psycho-behavioral obesity interventions among US multiethnic and minority adults

OBJECTIVE

The present review examines efficacious psycho-behavioral interventions in preventing weight gains or reducing weight among US multiethnic and minority adults as few studies were conducted to review such interventions to date.

METHODS

Data were examined from 24 controlled intervention studies, representing 23 programs and involving 13,326 adults. Studies were identified through manual and online search of databases that include MEDLINE, Academic Search Premier, ERIC, PsycARTICLES, SPORTDiscus, and CINAHL Plus.

RESULTS

Whereas one-component (n=5, d=0.08, 90% CI=-0.04, 0.35) and two-component interventions (n=13, d=0.22, 90% CI=0.05, 0.40) showed a low mean effect size, three-component interventions (n=6, d=0.52, 90% CI=0.39, 0.65) showed a moderate effect size. Interventions conducted in individual sessions (n=15, d=0.40, 90% CI=0.24, 0.56) showed a higher mean effect size than group interventions (n=9, d=0.08, 90% CI=-0.04, 0.30) although the confidence intervals overlapped.

CONCLUSIONS

The study results indicate that future obesity prevention interventions targeting multiethnic and minority adults might benefit from incorporating individual sessions, family involvement, and problem solving strategies into multi-component programs that focus on lifestyle changes.

Validation of a food frequency questionnaire measurement of selected nutrients using biological markers in African-American men

OBJECTIVE

To validate selected nutrients assessed by the food frequency questionnaire (FFQ) used in the Harvard cohort studies in an African-American group.

DESIGN

Blood aliquots were pooled for each decile of intake of two carotenoids and alpha tocopherol as measured by FFQ. These pooled samples were analyzed for nutrient content, and the resultant blood levels were plotted against the median for each decile of intake. In addition, adipose tissue samples taken from each man were analyzed for content of specific fatty acids. We calculated the Spearman correlations comparing intakes of specific fatty acids as percent of total fat intake, adjusted for energy intake, as measured by FFQ, with the percentage of the corresponding fatty acid in adipose tissue.

SUBJECTS AND SETTINGS

African-American men (N=104) with prostate cancer were recruited from a Detroit physician's practice and completed a detailed FFQ.

RESULTS

Comparing decile 10 with decile 1 intake of nutrients as measured by FFQ, there was a 32% higher blood level of lycopene, a 288% higher blood level of beta carotene and a 100% higher blood level of alpha tocopherol. The Spearman correlation coefficients between intakes of linoleic acid, alpha linolenic acid, long-chain n-3 fatty acids and trans fatty acid measured by FFQ and the corresponding adipose tissue levels were between 0.10 and 0.47.

CONCLUSION

The FFQ was able to distinguish meaningful differences in biochemical measurements of selected nutrients and presumably corresponding differences in the extremes of intake in African-American men with prostate cancer who were likely to be motivated to report accurately. However, the results found are similar to those found in other populations.

Insulin and cancer

Obesity has recently been linked to mortality from the majority of cancers. The insulin/insulin-like growth factor (IGF) system may partly explain this effect. The metabolic syndrome, associated with hyperinsulinemia, may modulate this effect. Recent evidence supports the role of insulin and IGF-1 as important growth factors, acting through the tyrosine kinase growth factor cascade in enhancing tumor cell proliferation. In addition, the metabolic syndrome associated with a chronic inflammatory state and accompanying cytokine abnormalities may also contribute to tumor progression. Growing links between insulin and the etiology as well as prognosis in colon, prostate, pancreatic, and, particularly, breast cancer are reviewed. Of particular concern is the evidence that elevated IGF-1 may interfere with cancer therapy, adversely affecting prognosis. The role of insulin is of concern because of the increasing levels of obesity and the associated metabolic syndrome. Weight gain, through typical Western diet; limited levels of activity; and, more recently, stress-related changes in neuroendocrine function may lead to insulin resistance and hyperinsulinemia. The opportunity for a multidisciplinary approach involving nutrition, exercise, and stress reduction in an integrative setting may be crucial to limiting the insulin-resistant state and improving cancer outcomes.

Methods to increase fruit and vegetable intake with and without a decrease in fat intake: compliance and effects on body weight in the nutrition and breast health study

Dietary patterns that involve a decrease in fat and an increase in fruit and vegetable (FV) intake have been suggested to decrease cancer risks. In this study, intervention methods to selectively modify dietary fat and/or FV intakes were developed. Compliance to the diets and the effects on body weight are shown, because both of these dietary changes can impact on and be confounded by changes in energy intake. A total of 122 women with a family history of breast cancer were randomized onto one of four diets for 12 mo. Counseling methods were devised to increase amount and variety of FV consumed with or without a decrease in fat intake using modified exchange list diets. Women on the low-fat and combination low-fat/high-FV diet arms decreased their fat intakes to approximately 16% of energy. Women on the high-FV and the combination low-fat/high-FV diet arms increased FV intakes to approximately 11 servings/day. Despite counseling efforts to maintain baseline energy intakes, mean body weight increased significantly by 6 pounds in women in the high-FV diet arm and decreased significantly by 5 pounds in women in the low-fat diet arm. Percent body fat also was increased in the high-FV diet arm and decreased in the low-fat diet arm. Body weight and percent body fat in the combination diet arm did not change significantly. Control of energy intake, therefore, appears to have been achieved only when the addition of FV to the diet was balanced by a decrease in fat intake and both dietary components were enumerated daily. Maintenance of energy intake, therefore, did not appear to be attained intrinsically when individuals were counseled to make changes in the composition of their diets.

Plasma carotenoids, tocopherols, and antioxidant capacity in a 12-week intervention study to reduce fat and/or energy intakes

OBJECTIVE

We examined plasma levels of carotenoids, tocopherols, and total antioxidant activity in women before and after dietary intervention to reduce fat and/or energy intakes. Dietary fat and energy may affect intake and bioavailability of carotenoids and tocopherols, and these micronutrient levels in turn can contribute to the antioxidant capacity of plasma.

METHODS

Women were randomized onto one of four diets for 12 wk: non-intervention, low fat (15% of energy from fat with maintenance of energy intake), low energy (25% energy reduction with maintenance of percentage of energy from fat), and combined low fat and low energy. Fasting plasma was available for analysis from a subset (n = 41) of women enrolled in the study.

RESULTS

Levels of carotenoids and tocopherols did not change significantly over 12 wk on any diet arm, despite a modest but statistically significant increase in fruit and vegetable intake in the women following the low-fat diet (from 3.3 to 5.2 servings/d excluding potatoes). Levels of Trolox-equivalent antioxidant capacity (TEAC), total cholesterol, and two major plasma antioxidants (urate and bilirubin) also did not change significantly. Of the individual micronutrients measured, lycopene and lutein/zeaxanthin correlated most strongly with TEAC values, and the correlation with lycopene was statistically significant before intervention.

CONCLUSION

The decreases in dietary fat and energy intakes in this study were quite large, but this did not appear to have detrimental effects on plasma micronutrient levels, nor did it appreciably affect plasma antioxidants. Because lycopene levels were significantly associated with plasma TEAC before intervention, interventions that increase levels of lycopene might be more likely to increase the antioxidant capacity of plasma.

Effect of participant motivation on rapid dietary changes in an intervention trial

BACKGROUND

Dietary intervention research with free-living subjects relies on the ability of study participants to meet their dietary goals within the study timeframe. Little is known about underlying factors affecting compliance.

METHOD

Here, we examined whether motivation to enroll in a trial of low-fat and/or energy-reduced diets influenced the ability of healthy women to reach their dietary goals quickly.

RESULTS

Of the women who had energy-reduction goals (n=43), the 18 with an altruistic reason for participation had a much higher energy reduction success rate at 4 weeks (83%) than the 25 who gave self-rewarding reasons (48%).

CONCLUSIONS

Education, body weight, family history of cancer and previous diet experience did not appreciably affect dietary outcomes. This observation suggests that the societal importance of the research should be stressed in strategies that seek to affect rapid reduction of energy intake in clinical trials.

Effect of low-fat and/or low-energy diets on anthropometric measures in participants of the women's diet study

OBJECTIVE

To compare the effects of low-fat, low-energy and combination low-fat/low-energy intervention on changes in six anthropometric measures in Caucasian and African-American free-living women.

METHODS

The effects of dietary counseling strategies for fat and/or energy reduction were examined on anthropometric measures in 86 pre-menopausal women, average BMI of 28 kg/m2, who participated in a 12-week intervention trial called the Women's Diet Study. The dietary goals were 15% of energy from fat and/or 25% reduction in energy intake, relative to reported baseline intake, using a 2 x 2 factorial design. Analysis of covariance models were constructed to evaluate changes in anthropometric measures over the 12 weeks of study.

RESULTS

The biggest difference by race was in women who were relatively heavier at baseline, in which case African-American women lost significantly less weight but decreased their waist:hip ratio to a significantly greater extent than Caucasian women. With regard to the effects of diet arm, weight loss varied depending on baseline weight, and in women with higher baseline weights, the combination low-fat/low-energy diet resulted in the most weight loss (6.7 kg, p < 0.05). Decreases in the other anthropometric measures at week 12 were more uniform across diet arms and did not depend on baseline values. After controlling for previous weight history and race, the decreases in BMI, percent body fat and waist circumference after 12 weeks were statistically equivalent with the low-fat, low-energy or combination low-fat/low-energy diets. The relatively greater decreases in percent body fat and waist circumference with the combination diet versus the low-fat or low-energy diets were not statistically significant.

CONCLUSION

The low-fat, low-energy and combination diets all resulted in similar and statistically significant decreases in BMI, percent body fat and waist circumference over 12 weeks of intervention. The extent of weight loss, however, varied depending on baseline weight, and the combination diet was the only intervention to result in significant weight loss for women who were heavier at baseline. This indicates that, although there may be an advantage for reducing dietary fat in initially heavier women, any of these counseling strategies could be effective for improving anthropometric predictors of health risks associated with overweight status. This is useful since flexibility in dietary choices may facilitate adherence to dietary counseling in some individuals.