The abstract is below but some comment first (informed from this and this)
the study found that exercise enhanced insulin sensitivity, particularly when meals eaten after the exercise session contained relatively low carbohydrate content. Enhanced insulin sensitivity means that it is easier for the body to take up sugar from the blood stream into tissues like muscles, where it can be stored or used as fuel. Impaired insulin sensitivity (i.e., "insulin resistance") is a hallmark of Type II diabetes, as well as being a major risk factor for other chronic diseases, such as heart disease.
Interestingly, when the research subjects in this study ate relatively low-calorie meals after exercise, this did not improve insulin sensitivity any more than when they ate enough calories to match what they expended during exercise. This suggests that you don't have to starve yourself after exercise to still reap some of the important health benefits.
Insulin Sensitivity is of course a "good thing" - it means you need less of it for it to have an effect. An excellent primer on insulin matters is here.
What I found interesting were these comments:
This study follows up on several previous studies that demonstrate that many health benefits of exercise are transient: one exercise session produces benefits to the body that taper off, generally within hours or a few days.
"Many of the improvements in metabolic health associated with exercise stem largely from the most recent session of exercise, rather than from an increase in 'fitness' per se," Dr. Horowitz said.
What do we make of this?
- The importance of consistency - regular training, might not make you "fitter" but each session is important.
- Every workout is important - we tend to think of junk sessions, but every one matters
- Exercise and nutrition go together - what you eat limits the effects of how you train.
- It is still all about hormones
- what type of workouts have the best effects - endurance, resistance, HIIT?
Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity.
The content of meals consumed after exercise can impact metabolic responses for hours and even days after the exercise session. The purpose of this study was to compare the effect of low dietary carbohydrate (CHO) vs. low energy intake in meals after exercise on insulin sensitivity and lipid metabolism the next day. Nine healthy men participated in 4 randomized trials. During the control trial (CON) subjects remained sedentary. During the other 3 trials, subjects exercised (65%VO2peak; cycle ergometer and treadmill exercise) until they expended ~800 kcal. Dietary intake during CON and one exercise trial (BAL) was designed to provide sufficient energy and carbohydrate to maintain nutrient balance. In contrast, the diets after the other 2 exercise trials were low in either CHO (LOW-CHO) or energy (LOW-EN). The morning after exercise we obtained a muscle biopsy, assessed insulin sensitivity (Si; IVGTT) and measured lipid kinetics (isotope tracers). Although subjects were in energy balance during both LOW-CHO and CON, the lower muscle glycogen concentration during LOW-CHO vs. CON (402+/-29 vs. 540+/-33 mmol/kg dw, P<0.01) coincided with a significant increase in Si (5.2+/-0.7 vs. 3.8+/-0.7 (mU/L)(-1)(.)min(-1); P<0.05). Conversely, despite ingesting several hundred fewer kcals after exercise during LOW-EN compared with BAL, this energy deficit did not affect Si the next day (4.9+/-0.9, and 5.0+/-0.8 (mU/L)(-1)(.)min(-1)). Maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. Carbohydrate deficit after exercise, but not energy deficit, contributed to the insulin sensitizing effects of acute aerobic exercise. Whereas maintaining an energy deficit after exercise augmented lipid mobilization.