Stress, appetite, and why muscle will not grow

Stress and rest are what almost everyone asks about. Start with one thing: make your bed time and your wake time the same. It helps sleep quality, and that shows up in how you perform, in the gym and in your head. You cannot dodge stress completely. You can lower it, and you can work with it. Learn to rest on your feet: walks, a day out. Sometimes rest is doing nothing: a nap, sitting still, a massage.

Short answer: In chronic stress you sit in fight-or-flight almost all the time. That can weaken immunity, take your appetite, and slow digestion. That system also pushes the body to break tissue down. If rest-and-digest rarely gets a turn, storing and growing get harder. Acute stress, such as a hard workout, is fine.

Two modes, and neither one switches off

Your body runs two branches of the autonomic nervous system. The sympathetic branch is fight or flight. The parasympathetic branch is rest and digest. If food sounds awful, that can be a sign the sympathetic side is dominating, tied to chronic stress.

Sympathetic, the short list that matters here:

• it cuts saliva,
• it speeds the heart rate,
• it speeds breathing,
• it suppresses digestion,
• it releases adrenaline and the rest of that chemistry.

It gets you ready to perform in a crisis. Basically, to fight or to run.

Parasympathetic:

• it lets muscles ease off,
• it slows the heart rate,
• it calms breathing.

The body answers stressors and the conditions around you this way. One of the two is only ever in the lead. Neither one is fully off while the other is fully on.

When a bear is chasing you, you need a faster heart and faster breathing so the muscles get fuel and oxygen. You need to be switched on (adrenaline), with enough fuel and glucose in the blood (cortisol). When you are on the sofa with a series on, the parasympathetic side leads.

Your physiology often cannot tell the bear from a boss shouting at you.

Acute stress is fine. Chronic stress is the problem.

Acute stress is all right. A training session is the obvious case. The body answers it by adapting. A measured dose, and next time that stressor is easier.

Chronic stress is the worse one. You are almost always in that fight mode. That can weaken immunity, take your appetite, and slow digestion.

Here is how stress and appetite connect.

• The sympathetic side pushes the body to break tissue down and release energy into the blood, so it is there for fight or flight.
• If the parasympathetic side rarely balances that, the body has a harder time storing and growing.
• For a lot of naturally thin people (the old word is ectomorph), the problem sits right here: the balance of the two branches, how they handle stress, and how sensitive they are to it.
• Under constant stress, with a lower appetite, they burn a lot and eat less. Staying lean is easier. Building muscle is harder.
• Muscle growth is not only how much muscle you build. It is also how much you break back down. A low blood sugar can start what is called gluconeogenesis.
• In that, the liver turns amino acids into blood sugar, glucose. On a strict diet those amino acids can come more from breaking down muscle than from food. If you are naturally thin and muscle will not come, look at stress and at your habits. It is likely to pay. The calorie side of keeping muscle is in build muscle in a calorie deficit.

Appetite that swings the other way, toward eating more, is a different problem, in cravings and hunger. The clock that makes the two branches behave is mostly sleep, in how much sleep do you need. A walk is the cheapest active rest I know, and the step target is in how many steps a day.

If stress, appetite or digestion are badly off and they stay that way, talk to your doctor.

Frequently asked questions

What is the difference between the two stress systems?

Fight-or-flight speeds the heart and the breath, suppresses digestion and releases adrenaline. Rest-and-digest lets muscles ease, slows the heart and calms the breath. One of them only leads. Neither one is fully switched off.

Is all stress bad?

No. Acute stress, such as a training session, is fine. The body adapts to it. Chronic stress is the one that costs you.

How do you lower stress?

Make bed time and wake time the same. Rest on your feet, with walks and days out, and sometimes do nothing: a nap, sitting still, a massage.

Why do some thin people struggle to gain muscle?

Often the balance of the two branches, and how sensitive they are to stress. Under constant stress, with a lower appetite, they burn a lot and eat less. Staying lean is easy. Building muscle is not.

Sources, so you can check:

1) No named study, DOI or PMID in the source article. The sympathetic and parasympathetic description, and the practical steps, are the explanation from that piece.

Martin Barna

Online nutrition and fitness coach. Since 2013 I have helped 600+ people lose fat and keep the result. Science, not crash diets.

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This article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.