A new study suggests that resistance exercise after a dinner meal is more effective at lowering triacylglycerols in the hours following dinner than resistance exercise before a dinner meal.
If you have been diagnosed as diabetic or pre-diabetic your doctor has probably told you that exercise can help slow the progression of diabetes. Does it matter when you exercise and, if so, when is the best time to exercise? A study published this month in the Journal of Applied Physiology attempted to answer this question by measuring insulin, glucose and triacyglycerols in the blood of thirteen patients diagnosed with diabetes who exercised before and after dinner (Postdinner resistance exercise improves postprandial risk factors more effectively than predinner resistance exercise in patients with type 2 diabetes, 2015. Timothy Heden, et al.).
The study found that resistance exercise following dinner did a better job of lowering risk factors in the blood than both exercise before dinner and no resistance exercise. The risk factors were measured in the blood before, during and after the exercise and meal protocol. Each of the thirteen participants partook in each of the three experimental conditions: dinner without exercise, dinner 20-30 minutes after resistance exercise and resistance exercise 45 minutes after dinner.
Exercise was found to lower postdinner insulin and glucose levels relative to the non-exercise control. However, whether the resistance exercise was performed before or after dinner did not produce a significant effect, although there is a slight decrease trend in glucose and insulin when exercise was performed after dinner. These results are displayed in the figure below. In contrast to that decrease trend, pre-dinner resistance exercise was found to significantly drop pre-dinner glucose levels relative to both non-exercise and postdinner exercise conditions.
With regard to triacylglycerols, post dinner resistance exercise was found to significantly lower total triacylglycerols in the blood in the hours following dinner. Specifically, VLDL-1 was found to be lowered in the post dinner exercise group relative to both no exercise and pre-dinner exercise. VLDL-1 is a very low density lipoprotein responsible for carrying packaged fats from the liver to the rest of the body. VLDL thats not picked up by the body’s tissues can be converted to unwanted LDL (low density lipoproteins) leading to atherosclerosis. VLDL-1 has also been linked to insulin resistance. The figure below illustrates changes in total blood triacylglycerols (TAG).
This study only addresses a small piece of the answer of when to exercise. What about lunch and breakfast? Is the change in triacylglycerols enough to make a difference in diabetes progression? How would these results change with aerobic exercise? If a person with diabetes is trying to decide whether to perform resistance exercise before or after dinner, this data suggests to do it after dinner. However, if a patient found that he or she was consistently putting off exercise until after dinner and then missing any exercise entirely, it would be advantageous to exercise before dinner. Indeed, well being was assessed through out the study. As soft evidence that exercise is an enjoyable activity, well being before dinner was higher in premeal exercisers. After dinner both exercise groups had significantly higher well being than the non exercise group.
Thus, we can conclude that whether exercise is performed before or after dinner glucose levels, insulin levels, triacylglycerol levels and general well being all stand to benefit from a dosage of resistance exercise.