Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status

Abstract

Background Obesity is a risk factor for postmenopausal breast cancer incidence and pre- and postmenopausal breast cancer mortality, which may be explained by several metabolic and hormonal factors (sex hormones, insulin resistance, and inflammation) that are biologically related. Differential effects of dietary composition on weight loss and these metabolic factors may occur in insulin-sensitive vs. insulin-resistant obese women. Objective To examine the effect of diet composition on weight loss and metabolic, hormonal and inflammatory factors in overweight/obese women stratified by insulin resistance status in a 1-year weight loss intervention. Methods and Results Nondiabetic women who were overweight/obese (n = 245) were randomly assigned to a lower fat (20% energy), higher carbohydrate (65% energy) diet; a lower carbohydrate (45% energy), higher fat (35% energy) diet; or a walnut-rich (18% energy), higher fat (35% energy), lower carbohydrate (45% energy) diet. All groups lost weight at follow-up (P < 0.0001), with mean (SEM) percent loss of 9.2 (1.1)% in lower fat, 6.5 (0.9)% in lower carbohydrate, and 8.2 (1.0)% in walnut-rich groups at 12 months. The diet × time × insulin resistance status interaction was not statistically significant in the model for overall weight loss, although insulin sensitive women at 12 months lost more weight in the lower fat vs. lower carbohydrate group (7.5 kg vs 4.3 kg, P = 0.06), and in the walnut-rich vs. lower carbohydrate group (8.1 kg vs 4.3 kg, P = 0.04). Sex hormone binding globulin increased within each group except in the lower carbohydrate group at 12 months (P < 0.01). C-reactive protein and interleukin-6 decreased at follow-up in all groups (P < 0.01). Conclusions Findings provide some support for differential effects of diet composition on weight loss depending on insulin resistance status. Prescribing walnuts is associated with weight loss comparable to a standard lower fat diet in a behavioral weight loss intervention. Weight loss itself may be the most critical factor for reducing the chronic inflammation associated with increased breast cancer risk and progression. Clinical Trial Registration NCT01424007 on http://www.clinicaltrials.gov.

Dietary fat: From foe to friend?

“…Another randomized controlled trial (RCT) in postmenopausal women tested a lower-fat, higher-carbohydrate diet (20% and 65% energy, respectively), a lowercarbohydrate, higher-fat diet (45% and 35% energy, respectively), and a walnut-rich higher-fat, lower-carbohydrate diet (18%, 35%, and 45% energy, respectively) for weight loss. All three diets led to weight loss at 12 months, with slightly higher weight loss in the lower-fat diet group (33). A meta-analysis of dietary intervention trials showed that low-fat diets were effective for weight loss under ad libitum conditions (36); however, this was published prior to recent carbohydraterestricted diet studies.…”

“…Conversely, highcarbohydrate diets containing whole grains and other high-fiber foods provide the preferred fuel for colonic bacteria, with less secondary bile acid production and greater production of butyrate and other shortchain fatty acids that lower inflammation, decrease cellular proliferation, and enhance expression of genes with antineoplastic properties. Low-fat diets may also decrease serum estradiol and increase sex hormone-binding globulin (32,33) and may reduce other breast cancer risk factors such as mammographic density (34), although the persistence of these effects remains unclear.…”

Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis

“…The flow of the study selection procedure which followed the literature search is summarised in Figure 1 Table 2 . Five trials [45][46][47][48][49] did not include LDL-C as an outcome; ten trials [50][51][52][53][54][55][56][57][58][59] were performed on participants with Diabetes mellitus and/or CVD; eleven trials [60][61][62][63][64][65][66][67][68][69][70] had less than 100 randomised participants; three [71][72][73] had duration < 6 months; two trials 74,75 did not report on SD or 95% CI; seven trials [76][77][78][79][80][81][82] were irrelevant with inappropriate intervention; and one trial 83 was dismissed based on high attrition rate and high risk of bias.…”

Does Nut Consumption Reduce Mortality and/or Risk of Cardiometabolic Disease? An Updated Review Based on Meta-Analyses

“…Tindall et al, 2019 [9] found no association between nut consumption and fasting glucose (weighted mean difference (WMD)-0.52 mg/dL (0.028 mmol/L); 95% CI −1.43, 0.38 mg/dL; I 2 = 53.4%) from a meta-analysis of 39 RCTs [58,61,63,[66][67][68]74,78,80,83,86,. Tindall et al, 2019 [9] found no effect of nut consumption on HbA1c (WMD 0.02%; 95% CI −0.01%, 0.04%; I 2 = 51.0%).…”

“…Tindall et al, 2019 [9] found no effect of nut consumption on HbA1c (WMD 0.02%; 95% CI −0.01%, 0.04%; I 2 = 51.0%). Tindall et al, 2019 [9] observed significant reductions in homeostasis model assessment of insulin resistance (HOMA-IR) (WMD −0.23; 95% CI −0.40, −0.06; I 2 = 51.7%) and fasting insulin (WMD −0.40 µIU/mL; 95% CI −0.73, −0.07 µIU/mL; I 2 = 49.4%) after nut consumption from meta-analyses of 19 RCTs [61,66,68,74,86,91,92,96,97,99,100,[103][104][105]107,109,110,114,117] and 28 RCTs [58,61,63,[66][67][68]74,86,[91][92][93][95][96][97][99][100][101][102][103][104][105]107,110,[112][113][114]...…”