Intramyocellular lipid content and insulin sensitivity are increased following a short-term low-glycemic index diet and exercise intervention.
Study Goal
The researchers aimed to determine the effects of a short-term low-glycemic-index (LGI) diet combined with aerobic exercise on intramyocellular lipid (IMCL) accumulation and insulin sensitivity in older, insulin-resistant adults.
Results Summary
The LGI diet combined with exercise improved insulin sensitivity and reduced HOMA-IR more than the high-GI diet, while also promoting lipid repartitioning from extramyocellular to intramyocellular stores. The LGI group showed greater reductions in EMCL and a higher IMCL/EMCL ratio, suggesting beneficial metabolic effects.
Population
Older, insulin-resistant adults (66 ± 1 years, BMI 33 ± 1 kg/m²).
Effective Dosage
Eucaloric diet (specific caloric intake not stated), combined with 60 min/day of supervised exercise at 85% HR(max).
Duration
7 days
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | decrease | BMI | older, insulin-resistant humans | -0.6 ± 0.2 kg/m(2) | decreased | #1 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | decrease | BMI | older, insulin-resistant humans | -0.7 ± 0.2 kg/m(2) | decreased | #2 |
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | increase | clamp-derived insulin sensitivity | older, insulin-resistant humans | 0.91 ± 0.21 mg·kg(-1)·min(-1) | increased | #3 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | increase | clamp-derived insulin sensitivity | older, insulin-resistant humans | 0.17 ± 0.55 mg·kg(-1)·min(-1) | increased | #4 |
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | decrease | HOMA-IR | older, insulin-resistant humans | -1.1 ± 0.4 | reduced | #5 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | decrease | HOMA-IR | older, insulin-resistant humans | -0.1 ± 0.2 | reduced | #6 |
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | increase | IMCL content | older, insulin-resistant humans | 2.3 ± 1.3 | increased | #7 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | increase | IMCL content | older, insulin-resistant humans | 1.4 ± 0.9 | increased | #8 |
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | increase | [IMCL]/[EMCL] ratio | older, insulin-resistant humans | 0.5 ± 0.2 | showed a robust increase | #9 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | increase | [IMCL]/[EMCL] ratio | older, insulin-resistant humans | 0.07 ± 0.1 | showed an increase | #10 |
short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) | decrease | [EMCL] | older, insulin-resistant humans | -5.8 ± 3.4 | demonstrated greater reductions | #11 |
short-term (7-day) high GI (HGI) diet and aerobic exercise training intervention (EX) | increase | [EMCL] | older, insulin-resistant humans | 2.3 ± 1.1 | showed a change | #12 |
The relationship between intramyocellular (IMCL) and extramyocellular lipid (EMCL) accumulation and skeletal muscle insulin resistance is complex and dynamic. We examined the effect of a short-term (7-day) low-glycemic index (LGI) diet and aerobic exercise training intervention (EX) on IMCL and insulin sensitivity in older, insulin-resistant humans. Participants (66 ± 1 yr, BMI 33 ± 1 kg/m(2)) were randomly assigned to a parallel, controlled feeding trial [either an LGI (LGI/EX, n = 7) or high GI (HGI/EX, n = 8) eucaloric diet] combined with supervised exercise (60 min/day, 85% HR(max)). Insulin sensitivity was determined via 40 mU·m(-2)·min(-1) hyperinsulinemic euglycemic clamp and soleus IMCL and EMCL content was assessed by (1)H-MR spectroscopy with correction for fiber orientation. BMI decreased (kg/m(2) -0.6 ± 0.2, LGI/EX; -0.7 ± 0.2, HGI/EX P < 0.0004) after both interventions with no interaction effect of diet composition. Clamp-derived insulin sensitivity increased by 0.91 ± 0.21 (LGI/EX) and 0.17 ± 0.55 mg·kg(-1)·min(-1) (HGI/EX), P = 0.04 (effect of time). HOMA-IR was reduced by -1.1 ± 0.4 (LGI/EX) and -0.1 ± 0.2 (HGI/EX), P = 0.007 (effect of time), P = 0.02 (time × trial). Although both interventions increased IMCL content, (Δ: 2.3 ± 1.3, LGI/EX; 1.4 ± 0.9, HGI/EX, P = 0.03), diet composition did not significantly effect the increase. However, the LGI/EX group showed a robust increase in the [IMCL]/[EMCL] ratio compared with the HGI/EX group (Δ: 0.5 ± 0.2 LGI/EX vs. 0.07 ± 0.1, P = 0.03). The LGI/EX group also demonstrated greater reductions in [EMCL] than the HGI/EX group (Δ: -5.8 ± 3.4, LGI/EX; 2.3 ± 1.1, HGI/EX, P = 0.03). Changes in muscle lipids and insulin sensitivity were not correlated; however, the change in [IMCL]/[EMCL] was negatively associated with the change in FPI (r = -0.78, P = 0.002) and HOMA-IR (r = -0.61, P = 0.03). These data suggest that increases in the IMCL pool following a low glycemic diet and exercise intervention may represent lipid repartitioning from EMCL. The lower systemic glucose levels that prevail while eating a low glycemic diet may promote redistribution of lipid stores in the muscle.