Why Does Heat Make Us So Bloated?
Every summer, the same thing happens. The temperatures creep up, you swap your routine for rosé on a terrace and a fridge full of “picky-bit” things that don't need cooking and somewhere around day three, you notice it. The bloating. The puffiness in your face. The legs that feel twice their usual size by evening. It's easy to dismiss it as something that just happens in the heat, something to push through. But there's real physiology behind it, and understanding it makes it a lot easier to manage.
We spoke to Clarissa Lenherr, nutritionist and gut health expert, and Olivia Johnson, lymphatic specialist, to get to the bottom of what's actually going on, in the gut and in the lymphatic system when the temperature rises.
The Gut: Why Digestion Slows Down in the Heat
It starts with blood flow. When the body is trying to regulate its own temperature, it redirects blood towards the skin,to help you sweat and cool down, and away from the digestive tract. That reduction in circulation slows the entire digestive process. Food sits in the gut longer, begins to ferment, and gas builds up. The result? Bloating.
"Heat also affects peristalsis” says Clarissa. “The contractions that move food through the gut, so you end up with slower transit time, more fermentation, more gas. And more bloating."
Which explains why it happens. But why do some people feel it so much more acutely than others? Clarissa points to gut sensitivity and baseline gut health as the key variables. People with IBS or a history of gut issues already have a more reactive enteric nervous system, which is sensitive to any physiological change, temperature included. Those with lower microbial diversity also tend to have less stable gut function overall, meaning any external stressor can push them over the threshold more easily.
Hormonal factors matter too, which is partly why women tend to be disproportionately affected. Oestrogen and progesterone influence gut motility, so anyone with hormonal fluctuations already has a more variable gut, and heat is just one more variable on top.
The Summer Diet Problem
We also tend to eat and drink very differently in the heat, and not in ways that help the gut. Cold drinks slow gastric motility. Ice cream delivers a simultaneous hit of fat, sugar, and often lactose - a near-perfect recipe for fermentation and gas production. Alcohol is a gut irritant at the best of times, but in the heat, dehydration concentrates everything in the colon and compounds the problem.
Then there's the meal structure issue. When we skip proper cooked meals, we often replace them with raw vegetables, fruit, or snack foods that are high in fermentable carbohydrates. Individually, each of these is manageable. Together, Clarissa says, it's a perfect storm.
“Most people are unknowingly making their bloating worse with every fizzy drink, every beer, every iced coffee they reach for to cool down”
What to Avoid and What to Reach for Instead
Clarissa's list of heat-bloat culprits might surprise you. Sparkling water is at the top, it feels refreshing, but you're essentially pumping gas directly into your gut. Beer and cider follow, both gut irritants and high in fermentable sugars. Large portions of raw cruciferous vegetables (yes, that includes coleslaw), ultra-processed snack foods with sugar alcohols and additives, and constant grazing rather than proper meals are all on the list too.
Instead: still water with electrolytes or a pinch of salt, cooked and cooled vegetables (which are actually easier to digest than raw), and small, frequent meals rather than large ones. Cooling herbal teas, peppermint and chamomile in particular, are underrated, she says, and genuinely helpful.
When to Take Summer Gut Discomfort Seriously
Heat bloating is usually temporary and mechanical. But Clarissa always asks her clients: is this just bloating, or is there more going on? Heat can act as a stressor that unmasks underlying gut-immune dysregulation that was already there, simmering beneath the surface.
She's also clear that the microbiome is involved in ways that go beyond the gut. Animal studies and emerging human data suggest that heat exposure shifts microbial composition in ways that mirror what's seen under psychological stress, affecting immune signalling, mood via the gut-brain axis, and nutrient absorption.
If serious gut discomfort is happening every summer and disrupting your quality of life, she's unequivocal: that's worth investigating. Seasonal patterns may indicate an underlying sensitivity that heat, dietary change, or both are triggering. It's your gut telling you something and it's worth listening to.
The Lymphatic System: Your Body's Drainage Network - and Why Heat Overwhelms It
The gut explains the bloating. But what about the swollen ankles, the puffy face, the general sense of heaviness that descends in a heatwave? That's a different system, the lymphatic system and it deserves equal attention.
"The lymphatic system is essentially the body's drainage and detox network," explains Olivia Johnson, Lymphatic Specialist. "Its job is to move excess fluid, waste, toxins, and immune cells around the body and back into the bloodstream for natural removal. It relies on movement, muscle contractions, hydration, healthy circulation or manual treatments like lymphatic drainage to keep everything flowing properly."
When temperatures rise, blood vessels and lymphatic vessels dilate, meaning more fluid can leak into the tissues. If the body becomes overwhelmed, through dehydration, prolonged heat exposure, hormonal changes, poor circulation, or pre-existing lymphatic sluggishness - that excess fluid has nowhere to go. The result is puffiness, swelling, heaviness, and water retention.
It's worth noting that heat isn't always a bad thing for the lymphatic system. Controlled heat exposure, such as saunas or acclimatisation to warmer climates, can actually stimulate circulation and temporarily encourage lymphatic flow, which is why many people feel less inflamed afterwards. It comes down to balance, hydration, and how well the body can regulate and adapt.
Water Retention, Oedema, or Lymphatic Swelling - Does the Distinction Matter?
Olivia is often asked whether the type of swelling matters for treatment, and the answer is yes - to a degree. Water retention tends to present as fluid you can feel under the skin, which can feel stretched or taut. After a lymphatic drainage session, she says, you can visually see the skin sit tighter against the body as pooled fluid shifts.
Oedema is a medical condition that exists on a spectrum, can be extremely painful, and is diagnosed by doctors rather than self-identified. Treatment is more complex and may include lymphatic drainage alongside pressotherapy, lifestyle interventions, and in some cases surgery.
Lymphatic sluggishness is more general, and its signs often feel unrelated to swelling at first glance: bloating, fatigue, brain fog, heaviness, adult acne. If something feels consistently 'off' and doesn't resolve, it may be worth considering whether lymphatic flow is part of the picture.
Movement Is Non-Negotiable, But the Right Kind Matters
The instinct in a heatwave is to stay still. The lymphatic system disagrees with that instinct fairly strongly.
Unlike the cardiovascular system, the lymphatic system has no central pump. It relies entirely on muscle contractions around lymphatic vessels to physically move fluid towards the lymph nodes for removal. Without movement, fluid stagnates. Daily movement isn't a nice-to-have for lymph health, it's the mechanism.
Olivia's top recommendation for hot weather specifically is swimming. The pressure of water against the skin, where the lymphatic system sits very close to the surface acts as a natural drainage tool. The added benefit: you don't overheat.
Certain plants have long been used to support lymphatic flow, and the evidence behind some of them is worth taking seriously. Cleavers, a traditional herb used in herbal medicine for centuries is considered one of the most direct lymphatic tonics, thought to help decongest sluggish lymph nodes and encourage fluid movement through the body.
Nettle is a reliable anti-inflammatory with a mild diuretic effect, useful for reducing fluid retention without depleting electrolytes. Dandelion works similarly, supporting liver and kidney function, which in turn takes pressure off the lymphatic system as a whole. All three can be found in tincture form, as loose leaf teas, or increasingly in more considered supplement blends. Worth adding to your routine, particularly in the weeks around summer travel.
On the Wellness Trends: Cold Plunges, Contrast Therapy, Dry Brushing
These tools are supportive, Olivia is clear, but they don't directly drain the lymphatic system. What they do is influence the conditions around it, improving circulation, helping fluid shift through the tissues, temporarily reducing inflammation.
Cold exposure tightens vessels and reduces puffiness. Heat increases circulation and eases fluid movement. Contrast therapy, alternating between the two, creates a gentle pump effect through repeated dilation and constriction. All useful. None of them are a replacement for movement and hydration.
Her view on nervous system alignment is worth noting here: if cold plunges make you feel terrible, they're not the answer for you. The nervous system is closely connected to lymphatic health, and doing something that genuinely makes you feel good matters.
Dry brushing is a different conversation. Olivia is candid: there isn't much robust evidence behind it, but she recommends it to her clients anyway. It encourages lymph flow and circulation, exfoliates the skin, and subjectively makes people feel lighter, particularly in the legs. Harmless, she says, and genuinely useful as a ritual if nothing else.
Manual lymphatic drainage, by contrast, is medically recognised and used in clinical settings for post-surgical swelling, specific medical conditions where lymphatic flow is compromised, and beyond. It's not just a wellness trend. Brazilian lymphatic drainage combines traditional lymphatic techniques with a stronger focus on visible body contouring effects, which is where some of the debate online comes in, but the foundational practice has real clinical standing.
Related Reading:
The Structural Shift: What Fillers Mean For Lymphatic Movement
I Tried LA’s Most Booked Out Lymphatic Massage And This Is What Happened
Building Long-Term Lymphatic Resilience
Olivia is often asked what people can do beyond the immediate fix, and she's clear that this is where the real work lies. Diet is a significant lever: reducing heavily processed foods, excess sugar, alcohol, and too much caffeine can all help, as these contribute to inflammation and sluggish fluid balance over time.
Regular movement is equally important, and cumulative. Even simple daily activity makes a real difference to how efficiently the lymphatic system moves fluid through the body.
And then there are the at-home practices worth building into a routine. Legs up the wall, genuinely effective, uses gravity to encourage drainage towards the lymph nodes. Professional lymphatic drainage sessions when needed. And if you're dealing with particularly heavy legs in a heatwave and need immediate relief, Olivia's recommendations are specific: Therabody compression jet boots to reduce swelling (not heated, crucially), Artah Cellular Hydration added to a glass of iced water for electrolyte replenishment, and a face sheet mask stored in the freezer for a few minutes before use to depuff and cool the face. Slightly indulgent, but her recommendation is 111Skin.
What About Flying?
Olivia notes that summer is her busiest time of year, much of it driven by pre and post-holiday demand. And there's a practical reason to book a session before you fly: by reducing fluid retention beforehand, there's simply less excess fluid in the body to be affected by changes in air pressure. The result is a noticeable difference in how swollen or heavy you feel during and after travel. Lymphatic drainage before a flight, it turns out, isn't just aesthetic preparation, it's intelligent body management.
The Edit
Heat bloating is real, it's physical, and it's more layered than simply drinking more water (though that helps). The gut and the lymphatic system are responding to genuine physiological stress and the choices we make in a heatwave, from what we drink to how much we move, compound or counter that stress in measurable ways.
The clearest message from both experts: the things we instinctively reach for in the heat, the cold sparkling water, the beer, the lying completely still on the sofa, are often the precise things making it worse. Swap the sparkling for still with electrolytes. Get in the pool. Put your legs up a wall. And if summer bloating is a seasonal pattern you've come to expect, it might be worth asking whether it's trying to tell you something.
The well loved list
Arrae Bloat Alchemy
HigherDose Supercharge Copper Body Brush
TheraFace De-Puffing Wand - Indigo
Words by Eleanor Hoath with experts Clarissa Lenherr and Olivia Johnson.
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