Why Heat Kills Your Appetite, and How to Eat Anyway

The first thing most travellers notice in a hot country is that they are not hungry. Not in an alarming way — just a general disinclination. Breakfast feels ambitious, lunch feels like a formality, and by evening you realise you have eaten a mango and half a bread roll since morning while walking, sweating and training in thirty degrees.

This is a genuine physiological effect, not a failure of appetite or discipline. It is also worth taking seriously, because the days when heat suppresses appetite most are usually the days your body has the most to recover from.

Why heat turns hunger down

Several mechanisms overlap.

The most important is blood flow. Thermoregulation is expensive. When core temperature rises, the body redirects blood towards the skin to shed heat by convection and evaporation, and away from the digestive tract. With splanchnic circulation reduced, digestion is a lower priority and the sensation of hunger fades. It is the same reason a heavy meal feels unappealing immediately after hard exercise.

Second, there is central signalling. Temperature-sensing regions of the hypothalamus sit close to the circuitry involved in appetite regulation, and body temperature is one of the inputs to feeding behaviour. Experimental work on eating in hot versus cold environments consistently finds that people eat less when hot and more when cold.

Third, thirst masquerades as fullness. Fluid losses in heat are large and easily underestimated. Sweat rates vary enormously between individuals and conditions, and can reach a litre or more per hour during sustained effort in heat. A body chasing fluid does not read as a body wanting food.

Why it matters more when you are active

For someone on holiday in the shade, eating a bit less in the heat is unremarkable. For someone training daily, it is the beginning of a spiral that is easy to recognise once you know the shape of it: appetite drops, intake falls below what the days demand, recovery suffers, sleep gets shallower, the next session feels harder, and appetite drops further because fatigue itself blunts hunger.

The signs to watch for are practical, not mystical. Sessions that feel disproportionately hard. Persistent light-headedness on standing. Poor sleep in an environment that should produce excellent sleep. Irritability with no cause. Any of these, particularly together, is a reason to pause and eat properly rather than to push harder. Persistent symptoms — or anything involving fainting, confusion, or a stopped period — are reasons to see a doctor, not to adjust a meal plan.

Eating anyway: seven practical moves

• Shift the big meal to the cool hours. Early morning and evening are when appetite returns. Much of tropical Latin America already eats a substantial breakfast and a proper lunch for this reason, then goes light at night.
• Drink your calories when you cannot eat them. Smoothies, jugos en leche, yoghurt with fruit, cold soups. Liquid food bypasses the reluctance that solid food triggers in the heat.
• Choose foods with water in them. Watermelon, papaya, cucumber, tomato, citrus, soups. They deliver fluid and energy at once, which is the exact combination the situation calls for.
• Eat smaller and more often. Four modest meals land better than two large ones when the gut is not enthusiastic.
• Cold, sharp, salty. Heat flattens appetite for rich and warm; it does not flatten appetite for lime, salt, acidity and chill. Ceviche exists for a reason.
• Replace salt, not just water. Sweat carries sodium. Drinking large volumes of plain water while eating almost nothing is a poor combination in heat; food is normally the simplest way to replace what is lost.
• Eat on a schedule when hunger goes quiet. On the hottest days, treat meals as part of the plan rather than as a response to a signal that heat has temporarily switched off.

Hydration, without the folklore

Two things are worth knowing and neither involves a fixed number of glasses.

Thirst lags behind fluid loss, particularly during exertion and as we get older, so it is a late signal rather than an early one. And requirements are individual — body size, sweat rate, humidity, acclimatisation and effort all move the figure enormously, which is why a universal daily target is not a useful instrument.

Urine colour is a rough, free indicator: pale straw generally suggests adequate hydration, dark yellow suggests catching up. It is imperfect, since some supplements and foods change the colour, but it is more informative than counting bottles. Anyone with a kidney or heart condition, or taking diuretics, should take fluid advice from a doctor, because for them the calculus genuinely differs.

Acclimatisation is real

The encouraging part: the body adapts. Over roughly one to two weeks of repeated heat exposure, plasma volume expands, sweating begins earlier and becomes more dilute, heart rate at a given effort falls, and the whole experience becomes noticeably less punishing. Appetite tends to come back with it. The first days in a hot climate are the hardest, and they are not representative.

A valley that is genuinely hot

Phoenix Oasis will open on 30 June 2028, on thirty hectares in Rivera, Huila — in the warm floor of the Magdalena valley, where afternoons are hot and the day naturally organises itself around that fact. The plan is for training to sit in the cooler ends of the day, for the middle to belong to shade, water and rest, and for the kitchen to lean on cold, hydrating, appetising food rather than hoping people will eat a heavy plate at two in the afternoon.

If you are heading anywhere hot before then, take one habit with you: eat breakfast like you mean it. More about how the days are being shaped is on the retreats page.