Not losing weight despite doing everything right: what to measure and test

“I am not losing weight” is one of the sentences most often repeated in an appointment and in a search box, almost always with the same continuation: “even though I do everything right.” You eat less, you walk more, you gave up soda, and the scale shows the same as a month ago. Before typing “why am I not losing weight” and ending up with a list of things to blame or the idea of a “slow metabolism,” it helps to sort out three things: how you are measuring, what we know about what we really eat, and what may be holding the process back that shows up in a blood test or a home measurement. This text is not going to tell you to eat less: it is going to tell you what to measure for four weeks and what to ask for afterwards.

One clarification before going on. If in recent weeks you gained several kilos without changing anything and you also have swelling of the legs or belly, or shortness of breath, this is not a logging matter: rapid gain can be a sign of fluid retention that needs a medical check soon.^[9] The rest of the text is for the usual situation: weight that does not come off despite the effort.

Why the scale does not answer the question

The number on the scale is the sum of fat, muscle, bone, water and what is in your gut, and only the first component is the one you want to change. Retained water and salt, the phase of your cycle and some medicines move the figure without the fat having moved: MedlinePlus lists fluid retention among the causes of weight gain and links it to menstruation and to certain medicines.^[9] That is why two weigh-ins one day apart say little.

Weight also has a weekly rhythm. In a study that followed 80 adults with 4,657 daily weigh-ins, weight was highest on Sunday and Monday and fell over the working days, week after week. The authors conclude that variations between weekends and weekdays should be considered normal and not signs of weight gain, and that long-term habits matter more than short-term splurges.^[3] If you weighed yourself on a Friday and then on a Monday, you compared two points on a wave, not a trend.

What does inform is the average of each week, always measured under the same conditions, and the line joining four consecutive averages.^[3] And next to weight, the waist. The British NICE guideline recommends keeping your waist below half your height and classifies waist-to-height ratio in adults with a BMI under 35: 0.4 to 0.49, healthy central adiposity; 0.5 to 0.59, increased; 0.6 or more, high.^[4] The waist can go down when the scale does not move.

What we do know: we record less than we eat

This is not an accusation; it is a finding repeated for decades with a reference method, doubly labeled water, which measures energy expenditure without relying on memory. In a pooled analysis of five US studies with 2,265 people, what people reported having eaten in 24-hour recalls came out on average 16 % below what their bodies had spent. A review of another 59 studies with 6,298 adults found that most reported under-reporting of between 20 and 30 %.^[2]

One more detail, not to be taken as a reproach: under-reporting grows with body mass index (with a BMI above 30, 7 % more) and is greater in people who worry about their weight.^[2] The more it matters to you, the more memory trims. It is not a character flaw, and the authors themselves ask for memories to be replaced with objective measurements.^[2]

The consequence is practical: replace estimates with records. What you eat, written down at the moment; steps, from the watch and not the feeling of “I moved a lot”; weight, under the same conditions. And look at the environment, not only willpower: the NIDDK places where you live and work, sleep, medicines and family history among the factors that affect weight.^[1] In Mexico that environment weighs heavily: in ENSANUT 2022, 75.2 % of adults aged 20 or older had overweight or obesity and 81.0 % had abdominal obesity (waist of 80 cm or more in women, 90 or more in men).^[10] You are not failing alone.

Four weeks of logging before the appointment

Four weeks is the minimum for the weekly average to separate from the noise of water, salt and cycle, and for the waist to have time to move.^[3] What matters is not the amount of data but that each measurement is taken the same way as the previous one.

The waist technique NICE recommends is simple: find the bottom of the ribs and the top of the hips, wrap the tape halfway between those two points and measure after breathing out naturally.^[4] Always at the same spot: one centimeter higher or lower changes the result more than a week of effort. The scale does not need to be expensive; it needs to be the same one. And on glucose: if you do not already measure it on medical advice, do not start pricking your finger for this log; if your doctor asks for it, here we explain what high fasting glucose means and what to record.

What can hold back weight loss and what clears it up

If after four weeks of honest logging neither weight nor waist moves, the question changes: it is no longer “what am I doing wrong” but “what is holding it back.” The NIDDK groups the causes into habits, environment, sleep, medicines, health problems and genetics,^[1] and MedlinePlus lists among the causes of weight gain without eating more hypothyroidism, Cushing syndrome, polycystic ovary syndrome, menopause, certain medicines and fluid retention.^[9] This table translates that list into what is recorded at home and what is ordered at the laboratory.

Insulin resistance

Insulin resistance means that the cells of muscle, fat and liver respond less to insulin, and the pancreas compensates by producing more.^[5] The NIDDK associates it with overweight, a large waist, inactivity, age 35 or older, family history of diabetes, polycystic ovary syndrome, sleep apnea and long-term use of glucocorticoids; most people have no symptoms at all.^[5] The most visible clue is a waist that will not budge and sleepiness or cravings two hours after eating, as we explain in this text on sleepiness after meals.

A nuance that saves frustration: the NIDDK explains that doctors do not usually measure insulin resistance directly, because that test is used mainly in research; what is measured is its footprint. A fasting glucose of 100 to 125 mg/dL or an HbA1c of 5.7 to 6.4 % corresponds to prediabetes, and the same institute recommends checking cholesterol and triglycerides, because blood fats rise when insulin stops working well.^[5] Many doctors add HOMA-IR, a calculation from fasting glucose and insulin that we explain in HOMA-IR: what it is and how it is calculated. If your triglycerides already came back high, here is what to review.

Thyroid

Hypothyroidism, a thyroid that works too little, appears on every list of causes of weight gain. The NIDDK describes its common symptoms: fatigue, weight gain, trouble tolerating cold, joint and muscle pain, dry skin or dry, thinning hair, heavy or irregular periods, slowed heart rate and low mood; it is much more common in women and in people older than 60, and it develops slowly.^[6] The same institute warns that fatigue and weight gain on their own do not necessarily mean a thyroid problem, and that confirmation is based not on symptoms but on blood tests.^[6]

On how much weight the thyroid explains, the American Thyroid Association is specific: in most people, hypothyroidism is related to about 5 to 10 pounds of gain (around 2 to 4.5 kg), and most of that weight is retained salt and water, not fat; once thyroid function is normalized, weight returns to what it was before and, from there, gaining or losing works the same as in anyone else.^[7] That is why the thyroid is checked, but it is not asked to explain 15 kilos.

The test is one: TSH, and if it comes back abnormal the doctor usually adds free T4. What each one measures is in thyroid panel: TSH, T4 and T3. If your main symptoms are tiredness or hair loss, we have a text for each: tired all the time and hair loss: which tests to ask for.

Sleep and stress

Sleep is the most underestimated factor in this conversation. The NIDDK recommends 7 to 9 hours a night for adults aged 18 to 64 and 7 to 8 from age 65, and explains that sleeping little is linked to weight gain because it may increase hunger and calorie intake.^[1] Long-term stress is on the same list of health problems that can lead to weight gain.^[1] None of this shows up in the blood; it shows up on the watch.

On cortisol, the stress hormone, it helps to lower expectations: measuring it “for stress” usually adds nothing. The test makes sense when the doctor suspects Cushing syndrome, a sustained excess of cortisol that is rare: the NIDDK estimates about 40 to 70 cases per million people in its spontaneous form, and notes that the most common cause is long-term, high-dose use of glucocorticoids. Its signs are different from weight that will not come off: a round face, fat between the shoulders, wide purple stretch marks, thin arms and legs.^[8] If the doctor suspects it, they order specific tests, such as 24-hour urine cortisol or late-night saliva cortisol; none is ordered on one's own initiative.^[8]

Perimenopause and menopause

Between 40 and 55 many women notice that the same routine stops giving the same result and that the waist grows even though weight changes little. MedlinePlus includes menopause among the hormonal changes that can explain weight gain without eating more, and links fluid retention to the phase of the cycle.^[9] At this stage the log of cycle, sleep and waist is worth more than any isolated hormone test; if hormones need measuring, your doctor will decide with your calendar in hand.

Medicines

Some medicines slow weight loss or reverse it, and they are almost never mentioned at the appointment because they are taken for another reason. The NIDDK lists classes: some medicines for epilepsy, depression or psychotic disorders; corticosteroids; some diabetes medicines; some blood pressure medicines, such as beta-blockers; and some antihistamines.^[1] MedlinePlus adds oral contraceptives.^[9] There is one rule: write down the medicine and the date, bring it to the appointment and do not stop anything on your own.^[9]

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) combines irregular cycles, excess hair or acne and, often, weight that accumulates at the waist and insulin resistance; the NIDDK includes it among the endocrine conditions that can lead to weight gain and among the factors that make insulin resistance more likely.^[1][5] If you recognize that set, the cycle log is the data that helps your doctor most; the tests are their choice.

What to do with the four weeks and when to repeat

At the end you will have four weight averages, four waists, 28 nights of sleep and 28 step counts. With that the decision becomes simpler:

• Weight goes down slowly, or the waist goes down even if weight does not: it is working. Keep going another four weeks before changing anything; the variation of one day or one weekend does not count.^[3]
• Neither weight nor waist moves, and the log was honest: it is time for the appointment, with the table in hand. Your doctor will decide what to order; the usual is fasting glucose, HbA1c, triglycerides, HDL and TSH.^[5][6]
• Weight goes up with an equally honest log: see a doctor too, with the list of medicines; if the gain was rapid or with swelling, do not wait to close the four weeks.^[9]
• The log came out irregular: conclude nothing; another four identical weeks are worth more than a test ordered without context.

Warning signs

Most people who are not losing weight have no disease behind it. But there are combinations that are not logged for four weeks: they are brought to a doctor without waiting.

• Rapid weight gain, several kilos in days or a few weeks, with swelling of the legs, feet or belly or with shortness of breath: it may be fluid retention, and MedlinePlus flags it as a reason to contact a doctor.^[9]
• A rounder face, new fat between the shoulders, wide purple stretch marks with thin arms and legs, especially if you take corticosteroids: these are the signs the NIDDK describes for Cushing syndrome.^[8]
• Intense thirst and frequent urination, together with tiredness or blurred vision: ask to have your glucose checked soon; here we explain what high glucose means.
• Periods that become very spaced out or disappear together with the change in weight, outside pregnancy: irregular periods are among the symptoms the NIDDK associates with hypothyroidism, and PCOS produces them too.^[6][1]
• Extreme tiredness with cold, very dry skin and a slow pulse, or the opposite, uncontrollable hunger with palpitations, tremor or sweating: both pictures appear among MedlinePlus reasons to see a doctor.^[9][6]

What to bring to the doctor

A weight appointment lasts minutes and usually ends in “eat less and move more” when the person arrives without data. With these six items it starts somewhere else.

1. The four-week table: the four weight averages, the four waists and the waist-to-height ratio.^[4]
2. Sleep and steps from the watch, as a weekly average and as nights below seven hours.^[1]
3. Full list of medicines and supplements, with dose and start date, including contraceptives and corticosteroids.^[1][9]
4. Cycle calendar with the days of bloating and cravings, if you menstruate, and since when your cycles changed.^[9]
5. Previous results for glucose, HbA1c, triglycerides, cholesterol and TSH, with dates, even if they are a year old.^[5][6]
6. Accompanying symptoms and since when: cold, tiredness, hair loss, sleepiness after meals, snoring, mood. They guide which test to order first.^[6]