Exercise as Medicine: Prescribing Movement for Metabolic Health

If a single medicine could lower blood pressure, improve insulin sensitivity, reduce liver fat, lift mood, improve sleep, preserve muscle and bone, reduce the risk of several cancers and lower mortality, with few side effects and little cost, it would be prescribed to almost everyone. Exercise does all of these things. Yet it is often recommended vaguely, as “get more exercise”, without the specificity, follow up or adjustment that any other treatment would receive. This article sets out how to prescribe it properly.

How much is enough

The World Health Organization’s 2020 guidelines recommend that adults do:

• 150 to 300 minutes of moderate intensity aerobic activity, or 75 to 150 minutes of vigorous activity, or an equivalent combination, each week;
• muscle strengthening activities involving major muscle groups on 2 or more days a week;
• for older adults, balance and functional training on 3 or more days a week to prevent falls;
• less sedentary time, replacing it with activity of any intensity.

The guidelines emphasise that some activity is better than none. The largest health gains come from moving from inactivity to modest activity. Meta analyses of daily step counts found that mortality risk fell progressively with more steps, levelling off at around 6,000 to 8,000 steps a day in older adults and 8,000 to 10,000 in younger adults, well within reach for many people.

What exercise does to metabolism

Glucose and insulin

Contracting muscle takes up glucose through pathways independent of insulin, and a single session of exercise improves insulin sensitivity for hours to days. Regular training increases muscle mass, mitochondrial capacity and glucose transporter content. In a study of people with type 2 diabetes, a 10 minute walk after each meal lowered post meal glucose more than a single 30 minute walk at another time of day.

Blood pressure

Aerobic, resistance and isometric exercise all lower blood pressure, with effects comparable to some single medicines in people with hypertension.

Lipids and liver

Exercise lowers triglycerides, modestly raises HDL cholesterol and reduces liver fat, even without weight loss.

Body composition

Exercise alone produces modest weight loss, but it reduces visceral fat, preserves muscle during weight loss and is one of the strongest predictors of maintaining weight loss.

Beyond metabolism

Physical activity reduces symptoms of depression and anxiety, improves sleep, supports cognitive function and reduces the risk of several cancers.

Cardiorespiratory fitness as a vital sign

Cardiorespiratory fitness, the capacity to take in and use oxygen during exercise, is one of the strongest predictors of mortality, comparable to or stronger than traditional risk factors such as smoking and hypertension. The American Heart Association has proposed that fitness be assessed as a clinical vital sign. It can be estimated from simple walking tests or questionnaires in routine practice. Improving fitness, even modestly, is associated with substantially lower risk.

Strength matters too

Resistance training is often neglected in favour of aerobic exercise. Yet muscle is the body’s largest site of glucose disposal, muscle strength predicts mortality and independence, and resistance training improves glycaemic control, bone density and function. It is particularly important for older adults, people losing weight and people at risk of sarcopenia. Grip strength is a simple marker associated with health outcomes.

Writing the prescription

The FITT framework, frequency, intensity, time and type, turns general advice into a specific plan.

2 further elements make the prescription work in practice: progression, increasing gradually as fitness improves, and enjoyment, choosing activities the person is likely to continue.

Starting safely

For most people, starting light to moderate activity such as walking is safe without formal assessment. Sports medicine guidance recommends medical clearance before starting vigorous exercise for people with known cardiovascular, metabolic or kidney disease or symptoms suggestive of these, and before starting any exercise in people with symptoms such as chest pain, unexplained breathlessness, palpitations or fainting.

Specific considerations include:

• Diabetes treated with insulin or sulphonylureas: risk of hypoglycaemia; glucose monitoring and adjustments may be needed.
• Diabetic complications: foot care with neuropathy; care with vigorous exercise in advanced retinopathy.
• Joint pain and osteoarthritis: exercise is beneficial; low impact options and physiotherapy guidance help.
• Frailty and falls risk: balance and strength training, ideally supervised initially.
• Pregnancy: activity is generally recommended for people without complications, with adaptations.
• Post exertional symptom exacerbation in conditions such as myalgic encephalomyelitis: graded exercise programmes may be harmful; specialist guidance on pacing applies.

Reducing sedentary time

Long periods of sitting are associated with adverse health outcomes, partly independent of exercise. Breaking up sitting with short bouts of standing or walking improves glucose and insulin responses in experimental studies. Practical steps include standing during calls, walking meetings, short walks after meals and “exercise snacks”, brief bursts of activity such as climbing stairs.

Helping people start and continue

1. Start with what matters to the person: energy, mobility, managing a condition, keeping up with grandchildren.
2. Begin where they are. For an inactive person, a 10 minute daily walk is a meaningful start.
3. Anchor activity to routines, such as a walk after dinner.
4. Address barriers: pain, time, safety, cost, confidence, caring responsibilities.
5. Use simple measures: steps, minutes, how far they can walk, how they feel.
6. Involve others: family, walking groups, physiotherapists, exercise professionals.
7. Review and progress at each follow up.

An illustrative case

A 58 year old man with type 2 diabetes, hypertension and knee pain has been told repeatedly to exercise but has not. He is sedentary, walks about 3,000 steps a day and says gyms are not for him. His priority is to avoid insulin.

His prescription starts with a 10 minute walk after dinner, the meal that raises his glucose most, which he monitors with home readings. After 3 weeks he sees his post dinner glucose fall and adds a walk after lunch. A physiotherapist provides a simple home strength programme with resistance bands for his legs and upper body, which also helps his knees. Over 4 months his steps rise to 7,000 a day, his HbA1c falls, his home blood pressure readings improve and he reports more energy. He still does not go to a gym, and he does not need to.

A prescription worth writing

Exercise deserves the same care in prescribing as any medicine: a clear dose, a plan for starting safely, attention to side effects and barriers, and regular review. Written this way, it is one of the most powerful and accessible treatments in metabolic medicine.