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Post-Exercise Appetite & Nutrition

Appetite

Our desire to eat is complex, influenced by various factors coming from both internal and external sources. The various signals are integrated within the hypothalamus of the brain where they act to either stimulate or suppress appetite. Because of the many factors involved, appetite is dynamic in nature and is influenced by our day-to-day lifestyle.

Within the body internal signals, such as hormones, provide feedback to the brain about the energy status of the body. For example, when energy stores are low, signals are sent to the brain to stimulate appetite. Similarly, when energy is in abundance signals are sent to suppress appetite. These hormones, referred to as appetite-regulating hormones, are responsible for influencing appetite within the hypothalamus of the brain.

In contrast, external influences, such as the sight and smell of food, are usually independent of the needs of the body. Further, these hedonistic factors often override the internal regulatory signals of the body. For example, have you ever been satisfied after a meal only to continue eating when offered desert? The smell and sight of a tasty food or even social influences can override any internal signals sent by the body. Thus, appetite is not merely a subjective feeling, but a complex integration of internal and external feedback signals influencing appetite.

Appetite-Regulating Hormones & Exercise

So how does exercise factor into the equation? Well first off, exercise can directly increase energy expenditure, which is the amount of energy required to complete a given activity. Another term for the energy requirement of the body is metabolism. In terms of appetite, after exercise internal feedback signals should stimulate appetite to replace the energy expended during exercise. However, this notion doesn’t always seem to hold true, as many athletes have reported suppressed appetite following exercise. This observation is puzzling as the obvious response of the body should be to stimulate appetite post-exercise.

A growing area of interest related to appetite is the influence that exercise may exert on appetite-regulating hormones. Recently, it has been shown that endurance exercise suppresses appetite by influencing appetite-regulating hormones. It appears that appetite suppression occurs after an acute bout of endurance exercise, meaning that the changes occur immediately rather than as a training adaptation over time.

Although various hormones have been measured following exercise, it appears that three main hormones are involved in appetite suppression. Two of these hormones, GLP-1 and PYY, originate from the gut and are involved in appetite suppression. After exercise, levels of GLP-1 and PYY are higher, leading to appetite suppression. The third hormone, ghrelin, is released from the stomach and acts to stimulate appetite. In contrast to the gut hormones, circulating ghrelin levels are lower following exercise, leading to suppression of appetite. Taken together, the effects of these three appetite-regulating hormones suppress appetite following exercise. There is further evidence that the intensity of exercise may also influence appetite. Studies comparing moderate versus high-intensity exercise have found a greater appetite suppression following high-intensity exercise. Although more evidence is needed, these early findings suggest that exercise and intensity play an important role in appetite.

The ability of exercise to influence appetite has several important implications. In terms of public health, the timing of exercise and food intake may be beneficial for weight management strategies. In terms of performance, athletes will need to consider appetite and post-exercise nutrition strategies for optimizing recovery. Since post-exercise nutrition is important for recovery and athletic performance, an athlete may have to develop strategies or find foods to consume even when not hungry.

Appetite and Post-Exercise Nutrition

The importance of post-exercise nutrition has been well established and is carried out by most athletes. Many sport nutrition companies market post-exercise or recovery products for athletes to consume after workouts. Despite this conventional knowledge, many athletes still delay or inadequately refuel following exercise. Thus, the importance of post-exercise nutrition cannot be overstated. 

During exercise the body primarily relies on glucose for energy, which comes largely from stored muscle glycogen. Post-exercise the body needs to replenish the glycogen used to fuel the activity. To do this, carbohydrate must be consumed after exercise. Failure to consume carbohydrates hinders recovery, as glycogen stores are not adequately replenished, and subsequent exercise is compromised. Think of it as the gas tank in a car: To drive, enough gas is needed in the.  After a trip, the gas tank needs to be refilled to prepare for the next trip. If you neglect to refill the tank, the next trip starts off with a half-full tank and you can’t go as far. Although more complex, the body works in a similar manner. If recovery doesn’t occur before the next exercise session then glycogen stores are even further depleted and performance is compromised. Over time this can cause a downward spiral leading to fatigue, overtraining syndrome, and injury.

Timing

A further consideration of post-exercise nutrition is timing. Immediately following exercise there is a 30-minute window where energy intake will be the most beneficial. Any carbohydrate consumed during the first 30-minutes will be used to re-synthesize muscle glycogen. After this time, carbohydrate intake is still beneficial but will not be used immediately for recovery. During this time it’s also important to include some protein too, as protein helps to repair damaged muscle fibers. Ideally, a ratio of 4:1, carbohydrates to protein is best for recovery. The timing of food intake can present a challenge for many athletes who may race or workout away from home or who simply don’t feel hungry following exercise. Thus planning and finding foods that taste good after exercise is important. 

Amount

How much carbohydrate do I need? The carbohydrate requirement varies by individual, but you should aim to consume around 1-1.5g/kg immediately following exercise. For example, a 150 lb (68kg) athlete should aim to take in about 70-100g of carbohydrate within the first 30 minutes following exercise. For protein needs, according to the 4:1 ratio, this same athlete should aim to take in around 20g of protein. Most food sources, such as sports drinks/bars, chocolate milk, yogurt, etc contain protein along with carbohydrate. See Table 1. for carbohydrate and protein content of some popular post-exercise foods.

Type

What types of foods are best to consume post-exercise? The best foods to consume post-exercise are foods that you find palatable and are familiar to you. The likelihood of consuming something post-exercise is much higher when that food tastes good. Liquids, such as energy drinks, chocolate milk, or smoothies tend to be easier to consume, especially when appetite is suppressed. My post-exercise drink of choice is chocolate milk.  I like it because it tastes good, is easy to sip on, and is easy to throw in my bag to take with me.

To find what works best for you I’d recommend you experiment with different types of foods to see what you like best. Some people can tolerate solid foods such as energy bars or a piece of fruit following exercise, while others can only tolerate only fluids. Both can provide adequate carbohydrate as long as they contain enough carbohydrate and are consumed immediately after exercise. See the list of Post-Exercise Foods to Try listed below.

Although many athletes know the importance of post-exercise nutrition they still neglect or delay food intake. The reason for this is most likely a combination of suppressed appetite following exercise and failure to plan ahead. Since nutrition can greatly impact performance especially when it comes to recovery, a good post-exercise nutrition routine is important to establish.  Awareness of the challenges associated with post-exercise nutrition, including appetite suppression and timing of intake, can help an athlete better prepare and develop strategies to optimize recovery. There is not a one-size-fits all approach to fueling after exercise, rather a framework of guidelines to help an athlete develop his or her optimal nutritional strategies. Often, trial and error is the best way to learn what works best. The only way you can go wrong is if you do nothing at all. So don’t be afraid to try! It can only help you in the long run.


Post-Exercise Foods to Try

· Chocolate Milk

· Fruit smoothie

· Yogurt with fruit & granola

· PB&J sandwich

· Sports bar

· Sports drink

· Pasta with cheese or red sauce

· Banana with peanut butter

· Cheese quesadilla

· Pretzels

· Graham crackers

 

Table 1. Carbohydrate & Protein Content of Various Foods.

Food

Amount

Carbohydrate (g)

Protein (g)

Banana with peanut butter

1 medium, 2T PB

35

9

Waffle

2 frozen

30

4

Pasta with red sauce

1 c pasta, ¼ c sauce

50

8

Brown rice

1 c cooked

45

4.5

PB&J Sandwich

2 slices bread, 2T PB, 2T jam

52

16.5

Cereal with milk

1 c cereal, ½ c milk

30

6

Energy bar, Clif

1 bar

45

9

Chocolate milk, lowfat

1 c

30

7.5

Yogurt, lowfat with fruit

1 c

45

10

Pretzels

10 twists

47

6

Crackers & cheese

16 wheat thins, 1oz cheese

21

10

Source: USDA Nutrient Data Laboratory, *Composition may vary among products

 

References

 

1.     Broom DR, Batterham RL, King JA, Stensel DJ. Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, and peptide YY in healthy males. Am J Physiol. 2009;296:R29-35.

2.     King JA, Miyashita M, Wasse LK, Stensel DJ. Influence of prolonged treadmill running on appetite, energy intake and circulating concentrations of acylated ghrelin. Appetite 2010;54:492-8.

3.     Stensel D. Exercise, appetite and appetite-regulating hormones: Implications for food intake and weight control. Annals Nutr & Metab., 2010;57(S2):6-42.

4.     Ueda SY, Yoshikawa T, Katsura Y, Usui T, Fujimoto. Comparable effect of moderate intensity exercise on changes in anorectic gut hormone levels and energy intake to high intensity exercise. J Endocrinol. 2009;203:357-64.

5.     Vatansever-Ozen S, Tiryaki-Sonmez G, Bugdayci G, Ozen G. The effects of exercise on food intake and hunger: relationship with acylated ghrelin and leptin. J Sport Sci Med. 2011;10:283-91.

 

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