A lower-carbohydrate, higher-fat diet reduces abdominal and intermuscular fat and increases insulin sensitivity in adults at risk of type 2 diabetes

Abstract

Background: Obesity, particularly visceral and ectopic adiposity, increases the risk of type 2 diabetes.

Objective: The aim of this study was to determine if restriction of dietary carbohydrate is beneficial for body composition and metabolic health.

Methods: Two studies were conducted. In the first, 69 overweight/obese men and women, 53% of whom were European American (EA) and 47% of whom were African American (AA), were provided with 1 of 2 diets (lower-fat diet: 55%, 18%, and 27% of energy from carbohydrate, protein, and fat, respectively; lower-carbohydrate diet: 43%, 18%, and 39%, respectively) for 8 wk at a eucaloric level and 8 wk at a hypocaloric level. In the second study, 30 women with polycystic ovary syndrome (PCOS) were provided with 2 diets (lower-fat diet: 55%, 18%, and 27% of energy from carbohydrate, protein, and fat, respectively; lower-carbohydrate diet: 41%, 19%, and 40%, respectively) at a eucaloric level for 8 wk in a random-order crossover design.

Results: As previously reported, among overweight/obese adults, after the eucaloric phase, participants who consumed the lower-carbohydrate vs. the lower-fat diet lost more intra-abdominal adipose tissue (IAAT) (11 ± 3% vs. 1 ± 3%; P < 0.05). After weight loss, participants who consumed the lower-carbohydrate diet had 4.4% less total fat mass. Original to this report, across the entire 16-wk study, AAs lost more fat mass with a lower-carbohydrate diet (6.2 vs. 2.9 kg; P < 0.01), whereas EAs showed no difference between diets. As previously reported, among women with PCOS, the lower-carbohydrate arm showed decreased fasting insulin (-2.8 μIU/mL; P < 0.001) and fasting glucose (-4.7 mg/dL; P < 0.01) and increased insulin sensitivity (1.06 arbitrary units; P < 0.05) and "dynamic" β-cell response (96.1 · 10(9); P < 0.001). In the lower-carbohydrate arm, women lost both IAAT (-4.8 cm(2); P < 0.01) and intermuscular fat (-1.2 cm(2); P < 0.01). In the lower-fat arm, women lost lean mass (-0.6 kg; P < 0.05). Original to this report, after the lower-carbohydrate arm, the change in IAAT was positively associated with the change in tumor necrosis factor α (P < 0.05).

Conclusion: A modest reduction in dietary carbohydrate has beneficial effects on body composition, fat distribution, and glucose metabolism. This trial was registered at clinicaltrials.gov as NCT00726908 and NCT01028989.

Keywords: PCOS; body composition; glycemic load; insulin secretion; insulin sensitivity; visceral fat.

Conflict of interest statement

Author disclosures: BA Gower and AM Goss, no conflicts of interest.

© 2015 American Society for Nutrition.

Figures

FIGURE 1

Change in IAAT over 8 wk during the eucaloric phase (A) and in total fat mass over 8 wk during the hypocaloric phase (B) in overweight/obese adults consuming a lower-CHO or lower-fat diet. Values are means ± SEMs. A: Lower-fat diet, n = 29; lower-carbohydrate diet, n = 34; B: lower-fat diet, n = 28; lower-CHO diet, n = 31. *Different from lower-fat arm, P < 0.05. Both panels were adapted from reference . CHO, carbohydrate; IAAT, intra-abdominal adipose tissue.

FIGURE 2

Loss of total body fat over 16 wk (8 wk eucaloric followed by 8 wk 1000-kcal/d energy deficit) in overweight/obese AA and EA adults consuming a lower-CHO or lower-fat diet. Values are means ± SEMs. EA lower-fat diet arm, n = 14; AA lower-fat arm, n = 14; EA lower-CHO arm, n = 18, AA lower-CHO arm, n = 13. Different lowercase letters indicate significant differences between groups. Within AAs, those who consumed the lower-CHO diet lost more fat than did those consuming the lower-fat diet (P < 0.05). Within the lower-fat diet groups, the difference between ethnic groups in fat loss was significant at P = 0.05. AA, African-American; CHO, carbohydrate; EA, European-American.

FIGURE 3

Serum glucose (A) and insulin (B) concentrations in overweight/obese adults after consumption of lower-CHO or lower-fat breakfast meals. Values are means ± SEMs. *Groups differ at that time, P < 0.05. Lower-fat diet, n = 29; lower-CHO diet, n = 35. Adapted from reference with permission. CHO, carbohydrate.

FIGURE 4

Changes in fasting serum glucose (A), fasting serum insulin (B), PhiD (C), and insulin sensitivity (D) from baseline to week 8 in women with polycystic ovary syndrome who consumed lower-CHO and lower-fat diets. Values are means ± SEMs. Lower-fat diet, n = 23; lower-CHO diet, n = 27. Different from baseline: *P < 0.05, **P < 0.01, ***P < 0.001. Adapted from reference with permission. CHO, carbohydrate; PhiD, dynamic phase serum insulin response to glucose.

FIGURE 5

Changes in IAAT (A), IMAT (B), total body lean mass (C), and total body fat mass (D) from baseline to week 8 in women with polycystic ovary syndrome who consumed lower-CHO and lower-fat diets. Values are means ± SEMs. Lower-fat diet, n = 23; lower-CHO diet, n = 27. Different from baseline: *P < 0.05, **P < 0.01, ***P < 0.001. Adapted from reference with permission. CHO, carbohydrate; IAAT, intra-abdominal adipose tissue; IMAT, intermuscular adipose tissue.