When physical activity increases, such as through starting a new running program or going to more gym classes, it’s not uncommon for people to notice they’re getting sick more often. While sleep, stress, and overall recovery all play a role, nutrition is a key (and often under-appreciated) factor that directly impacts immune function.
When energy demands suddenly rise, the body’s fuel and nutrient requirements also increase. If intake doesn’t rise to match this higher output, it can lead to low energy availability. In this state, the body prioritises essential functions like movement and exercise over other systems such as immune defence. Over time, this can make a person more susceptible to frequent colds, slower recovery from illness, and ongoing fatigue.
Carbs and Protein, Protein, Protein!
Carbohydrates are especially important. When we exercise more, carbohydrate stores are used up more quickly. If these stores are not replenished adequately, this can contribute to increased physiological stress and may negatively impact immune function. Including carbohydrates before and after exercise helps restore energy stores, reduce stress on the body, and support overall recovery.
Protein also plays a key role. As activity levels increase, so do the body’s needs for repair and recovery. Protein supports muscle repair but is also essential for the production and function of immune cells. Spreading protein intake evenly across meals and snacks throughout the day helps maintain both recovery and immune health. Supplements are generally not necessary, as most people can meet protein requirements through food alone.
Micro but Mighty
Micronutrients are another important piece of the puzzle. Nutrients such as iron, zinc, vitamin C, and vitamin D all contribute to immune function and energy production. People increasing their exercise load may be at greater risk of deficiencies if intake isn’t well balanced. A varied diet including fruits, vegetables, wholegrains, lean proteins, nuts, and seeds can help to meet these needs.
Hydration is also often overlooked. Even mild dehydration can place additional stress on the body, which may affect both performance and immune function. Regular fluid intake across the day, as well as during and after exercise, supports overall physiological balance.
Getting sick more often when increasing exercise is not just “bad luck” or a sign of pushing too hard, it can be a sign the body is under-fuelled. Prioritising adequate energy intake, along with consistent protein and nutrient-dense foods, can make a meaningful difference to recovery and immune function.
Written by Maddy Raymond, Accredited Practicing Dietitian
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