Constipation is one of the most frequently reported nuisances on GLP-1 therapy, and it has a fairly intuitive explanation: you are eating less food, drinking less fluid, and digestion is moving more slowly. Less in, slower through, less out.

The three nutrition levers

Fibre

Fibre intake usually falls automatically when portions shrink — fruit, vegetables, legumes and whole grains are often the first things crowded out by a protein-first plate. Rebuilding it gradually, from food where possible, is generally better tolerated than a sudden jump.

Fluid

Fibre without adequate fluid can make things worse rather than better. The two go together, and both tend to drop at the same time on a GLP-1.

Routine

Regular eating times, regular movement and not routinely ignoring the urge all support normal bowel function. Gentle daily walking is a reasonable and low-risk place to start.

Practical additions

• Add one fibre-containing food to a meal you already eat rather than redesigning your day
• Include a mix of fibre types — vegetables, fruit with skin where tolerated, legumes, oats, seeds
• Pair every fibre increase with a matching increase in fluid
• Keep meals at broadly consistent times
• Build in daily movement, even briefly

When it's not a nutrition question

Contact your prescribing clinician if constipation is severe or persistent, if you have significant abdominal pain, vomiting, no bowel movement for an extended period, blood, or unexplained changes in your symptoms. Do not start laxatives, fibre supplements or any over-the-counter product without checking with your clinician or pharmacist first — particularly alongside prescription medication.

The bottom line

Fibre, fluid and routine are the nutrition levers, and they work best applied together and gradually. Anything severe, painful or persistent is a conversation with your prescriber, not something to manage from an article.

The honest answer is: it depends on what your food is already doing, and nobody can tell you without looking at that first. Which is inconvenient, because it doesn't fit on a product label.

The case for paying attention

Vitamins and minerals arrive with food. When the volume of food falls substantially — and stays down for months — the amount of everything that travels with it falls too. That is a reasonable basis for checking whether your intake still covers your needs. It is not, by itself, a reason to buy a shelf of bottles.

What supplements can reasonably do

• Close a specific, identified gap between what you need and what you are eating
• Make a target more achievable — for example, protein on days when food is difficult
• Provide a consistent baseline where diet is genuinely variable

What they cannot do

• Replace the protein, fibre and overall structure of real meals
• Compensate for an intake that is far too low overall
• Substitute for resistance training when the goal is preserving muscle
• Diagnose or treat a deficiency — that requires clinical assessment

Safety matters more than usual here

Supplements interact with medications, with each other, and with existing conditions. More is not better — several nutrients have upper limits where excess causes harm. Anyone taking prescription medication, pregnant or breastfeeding, or living with kidney, liver, cardiac or thyroid conditions should review every supplement with their prescribing clinician and pharmacist before starting it.

How Sustayn approaches it

Your dietitian looks at what you are actually eating first. Supplements included with your membership are positioned to complement that plan and fill the gaps identified in it — they are a component of the programme, not the point of it. They are also always optional.

The bottom line

Reduced intake is a legitimate reason to look closely at nutrient adequacy. It is not a reason to self-prescribe. Get an assessment, then supplement the gap that assessment finds.

It is a strange problem to have. For years the difficulty was eating less; now the difficulty is eating at all. Many people on GLP-1 medications describe going most of a day without a hunger signal, then realising at 9pm that they've eaten a yoghurt and half a sandwich.

Hunger is no longer your measuring instrument

The medication works in part by blunting appetite signalling. That means the cue you have used your whole life to decide when and how much to eat has been deliberately turned down. Waiting to feel hungry is no longer a reliable way to get what you need.

The replacement is structure: eating on a schedule, to a plan, in amounts decided in advance rather than in the moment.

A workable framework

1. Anchor three eating occasions. Set rough times rather than waiting for a cue. They can be small.
2. Give each one a protein anchor. Decide the protein component first; everything else is built around it.
3. Add a nutrient-dense extra. Vegetables, fruit, dairy, legumes, whole grains — whatever you tolerate that day.
4. Keep two 'minimum days' in your pocket. Two specific, easy combinations you can manage even when nothing appeals.
5. Track for a short window, not forever. A few days of honest recording tells you and your dietitian more than months of guessing.

Small plates still need to be good plates

If your total intake has halved, the nutritional quality of what remains matters roughly twice as much. The same 400 calories can be a protein-containing meal with vegetables, or it can be a pastry. Both are fine occasionally; only one of them is a foundation.

When to raise it with someone

Struggling to eat anything for days at a time, losing weight far faster than expected, feeling faint or unusually weak, or being unable to keep fluids down are all reasons to contact your prescribing clinician rather than to push through. Nutrition strategy is our job; anything that feels medical is theirs.

The bottom line

Not being hungry is not the same as not needing food. When the signal goes quiet, the plan takes over — and the plan should be specific enough that you can follow it on your worst day, not just your best one.

A surprising amount of daily fluid comes from food — soups, fruit, vegetables, yoghurt, even bread. When you eat substantially less, you lose that contribution without noticing. Add a blunted thirst signal and days that get busy, and fluid intake can drop a long way below where it used to sit.

What under-hydration tends to affect

• Fatigue and low energy that feels out of proportion to your day
• Headaches, particularly in the afternoon
• Constipation, which fibre alone will not fix without fluid
• Dizziness or light-headedness, especially standing up quickly
• Concentration and mood

None of these is proof of dehydration on its own — they overlap with plenty of other explanations, including simply not eating enough. That is exactly why it is worth ruling out the easy variable.

Building a target you'll actually hit

General fluid recommendations vary with body size, climate, activity and medical conditions, and some conditions require fluid restriction. Rather than adopting a number from the internet, agree one with your dietitian or clinician and then make it structurally easy to reach.

1. Attach fluid to existing habits. A glass with each medication, each meal, on waking, and before bed.
2. Keep a visible container. Out of sight genuinely is out of mind when thirst is muted.
3. Count what counts. Water, milk, herbal tea, broths and most non-alcoholic drinks contribute.
4. Sip rather than gulp. Large volumes at once can feel uncomfortable with early fullness — and drinking a lot immediately before eating can crowd out food.
5. Watch the hot days and travel days. Requirements go up exactly when routine breaks down.

When to seek care

Persistent vomiting, inability to keep fluids down, very dark urine with reduced output, confusion, or fainting are medical concerns. Contact your clinician or seek urgent care rather than managing these at home.

The bottom line

Fluid is the easiest thing to lose track of and one of the easiest to fix. Set a target with a professional, attach it to habits you already have, and treat it as part of the plan rather than an afterthought.

When you lose weight, you don't only lose fat. Some proportion of the loss comes from lean tissue — muscle, connective tissue, and the water that goes with them. This is true of essentially every method of weight loss, including diet alone, surgery and medication. The question worth asking is not whether it happens, but what influences how much.

Why lean mass is worth protecting

Muscle is not just about appearance or athletic performance. It is what carries shopping up stairs, gets you out of a low chair, stabilises your joints, and — as you age — is closely tied to independence and fall risk. It also contributes to daily energy expenditure, which becomes relevant when you eventually move into maintenance.

The two levers that matter most

1. Adequate protein intake

Protein supplies the raw material for maintaining muscle tissue. In a calorie deficit, protein requirements are generally considered higher than they are at weight stability — precisely because the body is in a net-breakdown state and needs more input to offset it. This is the same reason the protein conversation comes up so often on GLP-1 medications: the deficit can be large and the appetite for protein-dense food is often the first to disappear.

2. Resistance training

Loading a muscle gives the body a reason to keep it. Resistance training — weights, bands, bodyweight, machines — is the signal that tells your body the tissue is being used. Protein without training, or training without protein, is only half the equation.

Supporting factors

• Rate of loss. Very rapid weight loss tends to come with a greater proportion of lean tissue. Slower is generally kinder to muscle.
• Sleep. Chronic short sleep works against recovery and against appetite regulation.
• Total energy intake. An extreme deficit stacked on top of an appetite-suppressing medication gives your body little to work with.
• Distribution. Spreading protein across the day, rather than concentrating it in one meal, is generally advised.
• Everyday movement. Walking and general activity support overall health, but they are not a substitute for resistance work when the goal is preserving muscle.

How would I know?

Scale weight alone can't tell you what you're losing. Practical signals include strength in the movements you train, how everyday physical tasks feel, and — where available — body-composition measurement over time. Any measurement is most useful as a trend, taken the same way each time.

The bottom line

Some lean mass loss is expected. Eating enough protein and loading your muscles regularly are the two things most consistently associated with limiting it. Neither requires anything exotic — but both require doing them for months, not weeks.

Most people starting a GLP-1 medication expect to eat less. Fewer expect how selectively they will eat less. Appetite doesn't fade evenly across the plate — for a lot of people, dense protein foods are the first thing that stops appealing, while softer, sweeter or more processed foods remain tolerable. The result is a smaller plate that has lost its most important component.

Why protein is the priority

Protein does several things at once during weight loss. It supplies the amino acids your body uses to maintain lean tissue, it is the most satiating macronutrient per calorie, and it supports the ordinary repair and immune functions that continue regardless of what you weigh. When total intake drops sharply, protein is the nutrient where a shortfall shows up soonest.

The other reason it matters: you cannot bank it. A day where you eat 30 grams instead of 100 is not something you make up by eating extra on Sunday. Consistency across the week is what counts.

How much do you actually need?

There is no single number that fits everyone. General population guidance sets a minimum to prevent deficiency, but people in an active weight-loss phase — particularly with a substantial calorie deficit — are usually advised to aim meaningfully higher than that minimum, with the target scaled to body size and activity.

Practical strategies when food isn't appealing

• Front-load the day. Appetite is often best in the morning and worst by evening. Put your largest protein serving at the meal you actually want to eat.
• Lead with protein on the plate. Eat the protein component first, before the volume-heavy sides fill you up.
• Choose softer, moister preparations. Slow-cooked, braised, poached or blended proteins are often far easier to tolerate than dry, dense cuts.
• Use liquids strategically. A protein-containing drink can be easier than a meal on a bad day — but as a supplement to eating, not a permanent replacement for it.
• Spread it out. Several smaller protein-containing servings across the day are usually more achievable than two large ones.
• Keep default options ready. Decide in advance what you eat on a low-appetite day, so the decision isn't made when you feel worst.

Signs your intake may be falling short

Persistent fatigue, feeling weaker in everyday tasks, hair shedding, slow healing, or losing weight much faster than expected are all worth raising — with your dietitian for the nutrition side and with your prescribing clinician for anything medical. None of these is diagnostic on its own, and none should be self-treated.

The bottom line

Eating less is the mechanism of the medication. Eating less protein is an avoidable side effect of that mechanism. Setting a target you can actually hit — and building a handful of default meals around it — is one of the highest-value things you can do in the first months on a GLP-1.

Any decision about starting, continuing, pausing or stopping a GLP-1 medication is a medical one, made with your prescribing clinician. What follows is not advice about that decision — it is about the nutrition side of what tends to change, so you can prepare rather than react.

Appetite comes back

The medication's appetite effect is not permanent. When it stops, the suppression stops with it, and hunger typically returns. For someone who has spent a year eating primarily because appetite was quiet, this can feel abrupt and destabilising.

It is also completely predictable — which means it can be planned for.

What actually carries over

Three things travel with you out of the medication phase, and all three are built during it, not after:

1. Muscle. Lean mass you protected on the way down is lean mass you still have. It supports strength, function and daily energy expenditure.
2. Habits. How you shop, how you assemble a plate, what your default meals are, how you handle travel and restaurants. Structure that never depended on suppressed appetite keeps working when appetite returns.
3. Skills and self-knowledge. Knowing your protein target, recognising your own patterns, having a plan for a difficult week.

Practical preparation

• Establish resistance training well before any transition, not as a response to it
• Know your protein target without having to look it up
• Have five to ten default meals you can make without deciding
• Agree what you will monitor, how often, and what would prompt you to seek support
• Keep your dietitian and your prescribing clinician in the loop about your plans

Weight regain is not a personal failure

Weight regain after stopping a weight-loss medication is a well-recognised pattern, not evidence of weak character. Treating it as a predictable physiological event — one you plan around with professional support — is far more useful than treating it as a moral one.

The bottom line

The medication phase is an opportunity to build the things that don't disappear when it ends. Protein, strength, structure and skills. Have the maintenance conversation early, and have it with people who know your case.

Nausea is common in the days after starting a GLP-1 or increasing a dose, and it tends to settle for many people as the body adjusts. While it is there, the goal shifts: not an optimal plate, just something tolerable, reasonably nourishing, and kept down.

The four variables worth adjusting

Portion size

Smaller amounts, more often, almost always sit better than a normal-sized meal. Think of it as several small opportunities rather than three obligations.

Texture

Soft, moist and smooth foods are usually easier than dry, dense or fibrous ones. Blended and slow-cooked preparations are often tolerated when the same ingredients in another form are not.

Temperature and smell

Cool or room-temperature foods release less aroma, and aroma is often the trigger. Many people find cold options far easier during a nauseated stretch.

Timing

Eating slowly, stopping before full, staying upright for a while afterwards, and separating large drinks from meals all tend to help.

Things that commonly make it worse

• Large meals, particularly late in the day
• Very high-fat or heavily fried food
• Strong cooking smells in a small space
• Lying down soon after eating
• Alcohol
• Pushing through a full feeling because it's 'mealtime'

When to contact your prescriber

Nausea that is severe, that stops you keeping fluids down, that comes with significant abdominal pain, or that persists rather than settling should go to your prescribing clinician. Dose adjustments, anti-nausea medication and any decision about continuing treatment are medical decisions — not something to work out through diet alone.

The bottom line

During a nauseated stretch, small, soft, cool and slow is the formula. Keep a short list of options that have worked before, so you are not deciding while you feel terrible.