Sunday, January 11, 2015

Working Out 45 Min After Dinner Improves Post-Meal Blood Glucose & Trigs More Effectively Than Working Out Before

Resistance training alone won't make up for a sloppy diet - no matter if you do it before or after meals.
I am not sure how feasible this is going to be for you, but if you are a type II diabetic or anyone concerned about the potential detrimental health effects of the rise in glucose and triglycerides after a meal, working out 45 minutes after dinner is the way to go.

Abnormally elevated postprandial glucose and triacylglycerol (TAG) concentrations are strong risk factors for cardiovascular disease (CVD) in patients with type-2 diabetes. Therefore, scientists expect that interventions that reduce postprandial glucose and TAG concentrations should lower the risk of CVD (Krook. 2003; O'Gorman. 2008).
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Previous studies have shown that acute exercise typically lowers postprandial glucose and TAG concentrations (Tobin. 2008) in patients with type-2 diabetes, but as Timothy D. Heden et al. point out, there is considerable heterogeneity in the responses with some individuals not experiencing beneficial changes in these risk factors (Gill. 2007; van Dijk. 2012).
"One potential explanation why some patients with type-2 diabetes do not have beneficial changes in postprandial glucose and TAG with acute exercise is because of the timing of the acute exercise session relative to meal consumption. Limited evidence suggests that the timing of aerobic exercise around a meal may be important and might explain why some individuals are exercise “insensitive” or “non responders”." (Heden. 2014) 
The only study to directly compare the effect of pre-meal and post-meal aerobic exercise on postprandial glucose concentrations in patients with type-2 diabetes showed that post-dinner, but not pre-dinner walking, lowered postprandial glucose concentrations (Colberg. 2009).
Figure 1: Previous studies indicate that aerobic workouts after meals have more beneficial effects on the potentially unhealthy increases in glucose or triglycerides (Collberg. 2009)
Although no study has directly examined the effect of exercise timing on postprandial TAG in patients with type-2 diabetes, there is evidence that exercise performed the day prior to a high fat meal has no effect on postprandial TAG responses (Dalgaard. 2004; Gill. 2007), while post-breakfast aerobic exercise reduced the postprandial TAG response (Tobin. 2008). Taken together, it appears that aerobic exercise may have its most powerful effect to lower postprandial glucose and TAG responses when performed after a meal, possibly because of slowed gastric emptying and/or greater skeletal muscle glucose and TAG uptake and utilization at this time.

The question that remained was: Is the same true for resistance training?

Since resistance exercise (RE) has a more pronounced long(er)-lasting effect on ones metabolism than aerobic training, the researchers from the University of Missouri tested the hypothesis that post-dinner RE, compared to pre-dinner RE, would in fact be more effective at improving two clinically important postprandial risk factors (glucose and 109 TAG) for CVD at a time of day when they are typically highest in obese patients with type-2 diabetes.

The standardized test workout consisted of the following exercises (in this order): leg press, seated calf raises, seated chest flyes, seated back flyes, back extensions, shoulder raises, leg curls, and abdominal crunches. All exercises were performed for three sets (1-2 min rest between sets) of 10-repetitions for each RE. During this session, the first set for each exercise was a warm-up set and the weight used was 50% of the participants 10-RM. After the warm-up set, the weight for the next two sets was the participants previously determined 10-RM.
Figure 2: Postrandial lipid response in the obese type II diabetics (Heden. 2014)
As you can see in Figure 2 the scientists suspicion was right, the postprandial workout (M-RE) had significantly more pronounced beneficial effects on the lipid metabolism of the type II diabetic subjects who consumed a standardized breakfasts (English muffin, cheddar cheese, one large egg, ham, hash brown, ketchup, and apple or orange juice) lunch (white bread, ham, mayonnaise, cheddar cheese, a granola bar, and apple or orange juice) and dinner meals (spaghetti noodles, spaghetti sauce with beef added, garlic bread, a lemon lime flavored soda, and 1.5 g of acetaminophen (to assess gastric emptying)) containing ~50% carbohydrate, 35% fat, and 15% protein.

Similar effects were observed for the insulin and glucose responses (see Figure 3) which were significantly improved and should thus complement the beneficial effects of the reduced triglyceride and very low density lipoprotein (VLDL) levels.
Figure 3: Changes in postprandial insulin and glucose levels (Heden. 2014)
Bottom line: Before we get to the actual interpretation of the result let me briefly point out that it would probably have been at least as effective if the subject had not been fed bull**** like ketchup, mayonnaise, granola bars, and purportedly healthy, but de facto obesogenic fruit juices. The unfortunate truth, however, is that 99% of the type II diabetics still eat like this. For them, the use of resistance training after each meal may be a possible, but unquestionably not practical way to ameliorate the unwanted cardiovascular side effects.

In view of the fact that most diabetics don't work at all, I am 100% convinced that the results of the study at hand have zero practical significance - even I wouldn't go work out after dinner only to lie in bed hungrily, thereafter, And if I did, I would raid the fridge later at night - certainly not a practice that's heart healthier than working out before dinner.

Speaking of which: Working out before dinner would also mean working out after lunch and could thus effectively help the increase in triglycerides and glucose after lunch. Not too bad either, right? | Comment on Facebook!
  • Colberg, Sheri R., et al. "Postprandial walking is better for lowering the glycemic effect of dinner than pre-dinner exercise in type 2 diabetic individuals." Journal of the American Medical Directors Association 10.6 (2009): 394-397. 
  • Dalgaard, Marian, Claus Thomsen, and Kjeld Hermansen. "Effects of one single bout of low-intensity exercise on postprandial lipaemia in type 2 diabetic men." British Journal of Nutrition 92.03 (2004): 469-476.
  • Gill, Jason MR, et al. "Effect of prior moderate exercise on postprandial metabolism in men with type 2 diabetes: heterogeneity of responses." Atherosclerosis 194.1 (2007): 134-143.
  • Heden, Timothy D., et al. "Post-dinner resistance exercise improves postprandial risk factors more effectively than pre-dinner resistance exercise in patients with type 2 diabetes."
    Journal of Applied Physiology (2014). Ahead of print.
  • Krook, Anna, et al. "Reduction of risk factors following lifestyle modification programme in subjects with type 2 (non‐insulin dependent) diabetes mellitus." Clinical physiology and functional imaging 23.1 (2003): 21-30.
  • O'Gorman, Donal J., and Anna Krook. "Exercise and the treatment of diabetes and obesity." Endocrinology and metabolism clinics of North America 37.4 (2008): 887-903.
  • Tobin, L. W. L., Bente Kiens, and Henrik Galbo. "The effect of exercise on postprandial lipidemia in type 2 diabetic patients." European journal of applied physiology 102.3 (2008): 361-370.
  • van Dijk, Jan-Willem, et al. "Exercise and 24-h glycemic control: equal effects for all type 2 diabetic patients?." Medicine and science in sports and exercise (2012).