If you are exercising to improve your insulin sensitivity, then Carbs after workouts are bad. Here’s the science (Nutrients. 2018 Jan 25;10(2). pii: E123. Post–Exercise Carbohydrate–Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults. Taylor HL, Wu CL, Chen YC, Wang PG, Gonzalez JT, Betts JA.)
In this study they put participants on a 90-minute treadmill at 70% of their VO2max. At the end they gave the participants either a placebo (no carbs) or maltodextrose that matched the caloric expenditure. Researchers then measured the glucose and insulin responses with an Oral Glucose Tolerance Test (OGTT) the following day and found that the participants who had the carbohydrates had reduced Insulin Sensitivity and increased blood glucose levels.
The practical conclusion of this is that to maximize Insulin Sensitivity it is best to both eat low carb and take no carbs after exercise. Decreased Insulin Sensitivity is one of the markers that lead to Diabetes and increasing Insulin Sensitivity is an important part of reversing Diabetes.
This study is the first to show that feeding carbohydrate to replace that utilized during exercise can reduce insulin sensitivity and glucose tolerance the next morning in healthy adults, when compared to a preservation of the exercise-induced carbohydrate deficit. Furthermore, carbohydrate replacement suppresses subsequent postprandial fat utilization. The mechanism through which exercise improves insulin sensitivity and glucose control is therefore (at least partly) dependent on carbohydrate
availability, and so the day-to-day metabolic health benefits of exercise might be best attained by maintaining a carbohydrate deficit overnight.
For those people who are not particularly concerned about their risk of getting Diabetes it’s worth noting that if they refill their Glycogen stores quickly with carbohydrates they are not burning fat. If they let the Glycogen stores be low then their body will burn fat.
Want to burn fat? Work out and don’t eat carbohydrates after working out.
Here’s a second study on the effects of post-workout carbs (Journal of the International Society of Sports Nutrition 201512:48. The effects of whey protein with or without carbohydrates on resistance training adaptations. Juha J. Hulmi, Mia Laakso, Antti A. Mero, Keijo Häkkinen, Juha P. Ahtiainen and Heikki Peltonen.) This study carefully compared three post-workout nutritions:
- Whey Protein Alone
- Carbohydrate Alone
- Whey Protein plus carbohydrates
All three groups in this study had gains in strength from the resistance training (RT). However, only the Whey Protein Alone had a decrease in fat mass. The study concluded:
This first long-term study supports the acute protein balance studies showing that adding carbohydrates to postexercise protein ingestion may not have large effect on the RT adaptations.
Whey proteins, however, increased abdominal fat loss and relative fat-free mass adaptations in response to resistance training when compared to fast-acting carbohydrates.
Therefore, if the main goal is to maximize fat loss responses to RT especially from abdominal area without compromising increases in muscle hypertrophy, whey protein instead of carbohydrates can be recommended for the postexercise nutrition.
Bottom line is that if you want to get leaner from resistance training, don’t eat carbs post-workout.