What to do when the diet is not working for you

People report feeling worse after changing their diet, and the internet response tends to be either that they are doing it wrong or that plant-based diets do not work.

Both are unhelpful. There is a diagnostic sequence.

First: are you eating enough?

The most common cause by a wide margin.

Plant foods are less energy dense. People who substitute without increasing volume end up in an unintentional deficit.

Symptoms: fatigue, feeling cold, poor concentration, low mood, irritability, poor sleep, in women menstrual changes, hair thinning, and preoccupation with food.

These are the symptoms of eating too little, and they are frequently attributed to the diet's composition rather than its quantity.

The check: track intake honestly for four days including a weekend. Compare to a rough estimate of requirements.

The fix: increase energy density — oil, nuts, nut butters, avocado, dried fruit — and eat more often.

Second: are you eating enough protein?

Related and distinct.

Symptoms of inadequate protein: poor recovery, hair loss, slow wound healing, muscle loss, persistent hunger.

The check: calculate your actual intake for a few days. Most people who think they are getting enough are not counting accurately.

The fix: a substantial protein source at every meal. Legumes, soy foods, and larger portions than feel necessary.

Third: are you supplementing?

B12 deficiency takes years to develop and produces fatigue, cognitive symptoms, numbness and tingling.

Vitamin D deficiency produces fatigue and muscle aches.

Iron deficiency produces fatigue, breathlessness and poor concentration.

Iodine deficiency affects thyroid function and produces fatigue, cold intolerance and weight change.

The check: blood tests. Full blood count, ferritin, B12, vitamin D, and thyroid function if symptoms fit.

The fix: supplement appropriately, based on results.

Fourth: is it the fibre?

A sudden large increase produces bloating, wind and discomfort for several weeks.

The fix: increase gradually, drink more water, soak and cook legumes properly, use spices traditionally paired with pulses, and persist — adaptation is what resolves it.

If symptoms persist beyond a couple of months, or include pain, weight loss or changes in bowel habit, that is a different matter requiring assessment.

Fifth: is it something else entirely?

The step most often skipped.

Fatigue, digestive symptoms and low mood are common and have many causes. A dietary change happening at the same time as symptoms does not establish that it caused them.

Conditions worth excluding: thyroid disease, coeliac disease, iron deficiency from another cause, diabetes, inflammatory bowel disease, depression, sleep apnoea, and simply a period of high stress or poor sleep.

Coeliac disease deserves specific mention: testing requires gluten to still be in the diet, so anyone who has removed it should be tested before or after a reintroduction, not during avoidance.

The step: see a doctor rather than adjusting the diet further.

Sixth: is the diet actually varied?

Diets that narrow over time — the same few foods, few vegetables, heavy reliance on processed alternatives, or restriction driven by rules rather than by nutrition — produce genuine problems.

The check: list what you actually ate last week. If it is fewer than fifteen or twenty distinct plant foods, that is worth addressing.

Seventh: is the eating disordered?

Worth naming, carefully and without accusation.

Restrictive eating patterns sometimes present as ethical or health-motivated dietary choices, and dietary restriction can also progress into something harmful without any prior intention.

Signs worth taking seriously: progressive narrowing of accepted foods, anxiety about eating outside your rules, avoidance of social eating, guilt after eating, food occupying a large amount of mental space, and weight loss you did not intend.

This is common, it is treatable, and speaking to a professional about it is not an admission of anything.

When the honest answer is different

Some people, after addressing all of the above, still feel better including some animal products.

That is a legitimate outcome. Individual variation exists, circumstances differ, and there is no obligation to persist with something that is not working.

The useful framing is not all or nothing. Substantially reducing animal products, sustained indefinitely, achieves more than a total change abandoned in frustration.

A diet that is mostly plants, with some animal food, is well supported by the evidence and is what a great many people arrive at.

The sequence, summarised

Eat more. Eat more protein. Take the supplements. Give the fibre time. Get blood tests. See a doctor. Widen the range.

Then, if it is still not working, adjust the diet to what works for you rather than to what you think you should be doing.

Persistent fatigue, unexplained weight loss, or digestive symptoms lasting more than a few weeks require medical assessment. Anyone with concerns about disordered eating should speak to a doctor or a specialist service.