Egg Diet: 5 Reasons Not to Try This Viral Trend

You've probably seen it: a video of someone cracking their third boiled egg of the day, captioned "lose 10kg in 10 days." The egg diet has been doing the rounds on TikTok for a few years now, and it keeps coming back. Searches for it have racked up well over 190 million views, and every resurgence brings a fresh wave of people wondering if this is finally the thing that gets the scale moving.

If you've been stuck at the same weight for months despite eating "well," it's an easy trend to fall for. But before you clear out the egg box, it's worth knowing what the diet actually asks of your body — and why it can be a particularly bad match if your thyroid is already under strain.

The egg diet works mainly because it's severely low in calories, not because eggs have any special fat-burning power. That level of restriction can lower your active thyroid hormone (T3), strip out nutrients your thyroid needs, and set you up for the weight to return once you stop. For most people, especially those with thyroid symptoms, it does more harm than good.

What Is the Egg Diet, Exactly?

The egg diet is a short, highly restrictive eating plan built almost entirely around boiled eggs, with a few low-carb extras like green tea, apples, or oats. A typical 10-day version has you eating three boiled eggs for breakfast with green tea, three more eggs with an apple for lunch, and three eggs with a small serving of oats or cornflakes for dinner. Some versions allow oranges or carrots as a snack. Depending on the exact plan, that adds up to roughly 900 calories a day — well under what most adult women need just to keep their organs running.

It isn't new. Versions of the "boiled egg diet" have circulated for years, but it found a second life on TikTok, where the #eggdiet hashtag has clocked up more than 68 million views. The British Dietetic Association specifically lists the boiled egg diet as an example of a "mono diet" — a pattern built around eating mostly one food — and groups it with the cabbage soup diet and chocolate diet as plans to be wary of.

Reason 1: The Calorie Level Can Backfire on Your Metabolism

A 900-calorie daily intake is a form of very low-calorie dieting, and your body treats it as a threat, not a health upgrade. When you eat that little, your body doesn't just burn fat quietly in the background. It reads the shortfall as a sign that food is scarce and starts slowing down how much energy it uses just to get by.

This isn't a fringe idea. A controlled study of 15 women found that those on a 400-calorie-a-day diet saw their active thyroid hormone, T3, drop by as much as 66%, while a hormone called reverse T3 — which effectively blocks thyroid hormone from working at the cellular level — rose by up to 27%. Even the women on a more moderate calorie-restricted diet saw T3 fall by up to 40%. In plain terms: the more aggressively you cut calories, the harder your body pumps the brakes on your own metabolism.

How Does Crash Dieting Affect the Thyroid?

Restricting calories tells your brain that energy is scarce, and your thyroid responds by converting less T4 into the active hormone T3. Your thyroid doesn't work in isolation. It's closely tied to how much food, and specifically how many carbohydrates, you're taking in. During calorie deprivation, the body shifts T4 away from active T3 and toward reverse T3, which acts like a brake pedal that reduces the activity of T3-dependent processes and lowers your resting energy use.

Endocrinologist Dr Antonio Bianco has described seeing this pattern repeatedly in patients who come in after a low-calorie diet: TSH stays normal-looking while T3 drops sharply, which can leave someone technically "in range" on a basic blood test while still feeling the effects of an underactive thyroid — fatigue, cold hands, sluggish digestion, and yes, a metabolism that resists further weight loss. If you already have hypothyroidism or Hashimoto's, layering a crash diet on top of an already-stressed thyroid system is asking for trouble. And if your labs have come back "normal" while you still feel awful, it's worth understanding what a fuller thyroid picture can show — something we cover in how to read your thyroid blood tests.

Reason 3: It Skips Nutrients Your Body Actually Needs

Building nearly every meal around one food, even a nutritious one, almost guarantees you'll fall short on other essentials. Eggs are genuinely good for you — they're a source of high-quality protein, B12, and iron. But a diet built almost entirely around them, with barely any wholegrains, legumes, or varied vegetables, is very low in fibre and wholegrain, according to registered dietitian Dr Frankie Phillips of the British Dietetic Association, who has said it "is not nutritionally balanced in any way" and isn't suitable for anyone with a medical condition.

That matters even more for thyroid health specifically. Converting T4 into usable T3 relies on minerals like selenium, zinc, and iron — the same nutrients a restrictive, single-food diet tends to squeeze out. Reporting on the trend has also flagged fatigue, mood changes, muscle weakness, and hair loss among people who've tried it, all of which overlap heavily with symptoms of an underactive thyroid. If you're already managing Hashimoto's or hypothyroidism, it's worth understanding which minerals actually support your thyroid before cutting out entire food groups to chase a number on the scale.

Reason 4: The Weight Comes Off Fast — and Tends to Come Back Faster

Rapid weight loss on a very restrictive diet is mostly water and muscle at first, not fat, and it's notoriously hard to keep off. The BDA's own guidance on fad diets warns that this kind of rapid loss is often lean muscle and fluid loss instead of body fat, and that when food groups are cut out and hunger cues are ignored, it tends to create cycles of weight loss followed by weight regain.

Registered dietitian Dr Duane Mellor, who has reviewed the trend, put it simply: "It is a quick fix. It will not improve your health long term." Once you stop eating 900 calories a day and go back to normal eating, your body — now running on a slower metabolism thanks to Reason 1 — is primed to regain the weight, sometimes with a little extra alongside it. If under-eating and stalled weight loss is a familiar cycle for you, it may be worth reading about thyroid-related weight resistance rather than reaching for another short-term fix.

Reason 5: It Can Feed a Rocky Relationship With Food

A diet this rigid can push you toward all-or-nothing thinking about food, which tends to outlast the diet itself. Eating the same three meals for ten days straight, with no flexibility for a birthday, a bad day, or simply feeling hungrier than the plan allows, sets up an unforgiving standard. People following the trend have described feeling nauseous and unwell partway through, and some have openly admitted breaking the diet out of necessity — hardly the confident, in-control experience the videos promise.

This pattern of restrict-then-rebound is exactly what dietitians warn does the most lasting damage: not just to your metabolism, but to your sense of trust in your own hunger and fullness cues. Chronic under-eating also keeps your body in a low-grade stress state, and stress itself is closely linked to thyroid function — something we've written about in why TSH can stay high even when you're doing everything "right".

So Are Eggs Themselves the Problem?

No — and this is an important distinction. Eggs have had a complicated reputation for decades, mostly over dietary cholesterol. That's shifted: the American Heart Association's updated 2026 dietary guidance states that moderate egg consumption can be included as part of a heart-healthy dietary pattern, and dietary cholesterol is no longer treated as a primary target for heart disease risk for most people.

The issue was never the egg. It's the framework built around it — three meals a day of almost nothing else, at a calorie level that's unsustainable for more than a week or two. Eggs deserve a place in a normal, varied diet: as a protein source alongside vegetables, wholegrains, and healthy fats, not as the entire meal plan.

The Bottom Line

The egg diet promises a fast fix, but the mechanism behind it — severe calorie restriction — is the same one that can quietly slow your thyroid, strip out key nutrients, and set you up to regain the weight. If you're dealing with genuine weight resistance, especially alongside thyroid symptoms, a crash diet almost always makes the underlying problem worse, not better.

If you've tried diet after diet and your weight still won't budge, it might not be about willpower — it could be about what's actually happening with your thyroid and metabolism. Book a discovery call to talk through what's really going on, without judgement and without another restrictive meal plan.

Frequently Asked Questions

Is the egg diet safe for someone with an underactive thyroid?

It's not advisable. The combination of very low calories and a lack of key thyroid-supporting nutrients like selenium and zinc can make hypothyroid symptoms worse rather than better. If you have a diagnosed thyroid condition, talk to your GP or a registered nutrition professional before starting any restrictive diet.

Why did I lose weight quickly on the egg diet, then gain it back?

Fast initial loss on very low-calorie diets is largely water and muscle rather than fat, and a slowed metabolism from calorie restriction makes regain more likely once normal eating resumes. Sustainable fat loss tends to happen more gradually, alongside adequate protein and strength-supporting nutrition.

How many calories does the 10-day egg diet actually provide?

Most versions work out to roughly 900 calories a day, depending on portion sizes and extras like fruit or oats — well below typical adult energy needs.

Are eggs bad for cholesterol?

Current guidance, including the American Heart Association's 2026 update, treats moderate egg consumption as compatible with a heart-healthy diet for most people. The bigger influences on blood cholesterol are saturated fat and fibre intake across the whole diet, not eggs specifically.

Sources

• British Dietetic Association — Fad diets
• Diabetes.co.uk — Egg diet trending on TikTok labelled as 'dangerously restrictive'
• Belfast News Letter — A ten-day egg diet has gone viral on TikTok
• Wadden et al., 1990, International Journal of Obesity — Effects of a very low calorie diet on weight, thyroid hormones and mood (PubMed)
• Paloma Health — Can Crash Dieting Cause Hypothyroidism?
• Frontiers in Endocrinology — Editorial: Thyroid hormones and diet
• Patient Care Online — Impact of Diet and Calorie Restriction on TSH Levels in Hypothyroidism
• Empirical Health — Eggs are now officially healthy