Should you change how you eat when you exercise?
Are you starting a new workout routine? In nutritionist Rhiannon Lambert’s new book, The Science of Nutrition, she shares her advice on how to support that extra movement through your food choices.
Anyone who’s getting more serious about fitness can learn from sports nutrition for elite athletes: eat the right balance of food groups for your personal training goals.
You need enough carbs
Carbohydrate is the main fuel for any exercise; it promotes strength and endurance, delays muscle fatigue, and speeds up recovery, meaning fewer injuries. It is converted to glucose and excess is stored as glycogen in the liver and muscles, providing instantly available energy. The longer and/or more intense the training, the faster glycogen depletes and fatigue can set in.
Daily carbohydrate needs
This is measured in grams by kilo of body weight, based on your individual activity level. To find this out, multiply your weight in kilograms by the grams of carbs you think you need – a moderately active woman who weighs 65g needs around 325-455g of carbs a day.
Low intensity: 3-5g
High: 1-3 hours moderate-high intensity 6-10g
Very high: 8-12g
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Protein is essential
Protein’s primary role is to build, and rebuild, muscle. Aim to eat 1.2g–2g per kilo of body weight daily: in the lower range for endurance and higher for strength training.
Fats are still important
Dietary fat must be converted into fatty acids before being taken up by muscles; it acts as support fuel during low-intensity endurance exercise like long-distance running, when glycogen runs low. Slower availability is also why you should avoid eating fats just before training. At least 20% of overall calorie intake should come from healthy fats.
Signs that your diet isn’t meeting your energy needs include fatigue, poor sleep quality, and irregular bowel movements.
Should you add supplements?
If you regularly run or cycle long distances, build muscle strength at the gym, or otherwise train hard, supplementing a healthy, balanced diet can be a good way to fill in nutritional gaps, get extra fuel on workout days, or boost performance.
For most people who visit the gym or play sports recreationally, supplements aren’t necessary; intense exercise increases the body’s need for certain nutrients, but the International Olympic Committee says even elite athletes should for the most part be able meet their needs by eating a balanced diet. Supplements can be a useful addition to enhance performance, although an excess can potentially cause stomach pain, nausea, and constipation.
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An unexpected superhero
Beetroot increases nitrate levels in the blood, which then helps to dilate blood vessels and regulate blood pressure so more nutrients and oxygen can reach muscles during exercise, allowing you to sustain higher levels of power for longer. It should be drunk two-to-three hours before training. Nitrate is also found in vegetables like spinach, rocket, broccoli, and cabbage.
Only those with high energy requirements need to supplement protein. Whey protein is derived from cow’s milk; evidence suggests it’s the best form of protein to take after exercise, being absorbed by the body more quickly than others such as casein or soya. (Plant-based supplements combine soya, pea, and rice.) While it’s also a good source of leucine, studies show no evidence of greater muscle growth over 24 hours from taking whey protein, as opposed to eating a normal, balanced diet.
The new go-to
Creatine is found in muscle cells and supplements have proven effectiveness in increasing strength and power, especially for activities involving explosive movements. Red meat, fish, and poultry contain only small amounts of creatine, so supplementing is an option for boosting performance, and for vegetarians and vegans. Of the many types available, creatine monohydrate appears to be an effective option.
Should you eat before or after exercise?
Your goal is to have enough stored glycogen from carbohydrates when you start training to sustain performance throughout. If you exercise first thing, glycogen in the liver has been depleted overnight, although some is still present in muscles if your diet generally contains enough carbohydrate. Exercising on a full stomach can be uncomfortable, as blood is directed away from your digestive system.
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The consensus is to eat a meal two to four hours before working out, where possible. An ideal pre-workout meal is mainly carbohydrate with some protein and a little fat; for example, salmon, white rice, and vegetables roasted in olive oil. If you train early and don’t have the time or appetite, try a more carb-heavy meal the night before. If you’re exercising sooner, or need to top up, a snack like white toast and honey or fruit salad one to two hours beforehand gives a burst of energy for fuel and is quickly absorbed. If you have less than an hour, stick to liquids like smoothies or sports drinks. Experiment to find the optimal timing for your activity, schedule, and digestion.
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While experts no longer believe refuelling must happen within a 30-minute “anabolic window”, it can be a good idea for recreational athletes to refuel within a couple of hours of exercise. Glycogen levels replenish at 150% of the normal rate during this time, and muscle cell membranes are more permeable so they can absorb more glucose to restore glycogen levels faster. Combining a small amount of protein with carbs post workout has been shown to more effectively promote glycogen recovery than carbohydrates alone. Flavoured milks, smoothies, and fruit yogurts all tick these boxes. Choose the fat and sugar content based on your individual body composition and energy needs.
If your training is mainly strength based, or if you’re training at a high intensity, there is evidence that adding 15g–25g of protein to a post-workout meal or snack can reduce muscle soreness and promote muscle repair. (A 150g serving of edamame beans would provide this.) Otherwise, follow your food preferences, appetite, and what sits comfortably in your stomach after exercise, and eat when you feel hungry. Overall daily energy and macronutrient intake is the priority; provided you consume enough calories, carbs, and protein over a 24-hour period, your muscles should recover before exercising again.
Extracted from: The Science of Nutrition: Debunk the Diet Myths and Learn How to Eat Well for Health and Happinessby Rhiannon Lambert. Published by DK, 30 December, £20.
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