Weight-loss diet: how to lose fat and keep it off

How long does it take to lose weight?

About half a kilo of fat per week is the pace we suggest in consultations. Five kilos take about ten weeks; ten kilos, four or five months. Weight often drops more than expected in the first week, and much of that loss is water, so it is not a useful way to calculate your pace.

It is better to set your goal as a percentage of your current weight. European guidelines on managing obesity in primary care explain that losing 5 to 10% of your starting weight already brings clear health benefits [2]. If you weigh 80 kilos, that is 4 to 8 kilos; if you weigh 100, it is 5 to 10.

With that loss, blood pressure, blood test results and your knees change before your clothing size does. This is the part that is rarely mentioned. The same guidelines point out that losing as much as possible in the shortest time is not the key to treatment [2].

There are two points worth knowing from the outset. First, the less weight you have to lose, the slower it goes, and that does not mean you are doing anything wrong. Second, you cannot choose where you lose fat, so there is no separate plan for your belly and another for your legs.

How to divide your plate

It is the only rule you need to learn, and it works for lunch and dinner. It is about proportions, so there is nothing to weigh.

• Half vegetables, raw or cooked. They fill you up with very little energy.
• A quarter protein, at both lunch and dinner.
• A quarter carbohydrates, preferably wholegrain.

To lose weight, the only change is that the carbohydrate portion is smaller than you would usually serve, but it does not disappear. If it does, you reach dinner feeling ravenous. The Agencia Española de Seguridad Alimentaria y Nutrición also lowers the upper limit for cereal servings when calorie intake needs to be reduced [1].

Here is what a full day could look like, with approximate amounts. Breakfast is coffee with milk and 60 g of wholemeal bread with avocado and tomato, then a piece of fruit mid-morning. For lunch, a salad with lentils and grilled salmon, followed by a yoghurt for an afternoon snack. Dinner is courgette soup, a mushroom omelette and bread.

If you cook, make extra: tomorrow’s serving is already prepared, and that can save dinner on a difficult day.

What is the best diet for losing weight?

The best weight-loss plan is one you can sustain.

The evidence supports this. In 2025, the British obesity guideline (NICE) reviewed all types of dietary plan (low-fat, low-carbohydrate, very-low-carbohydrate and intermittent restriction). It could not recommend one over the others, because the studies did not distinguish between them [3]. All created an energy deficit, each in its own way.

Three practical conclusions follow.

• Keto, food-combining and pineapple diets are different ways of eating less, with no advantage over the others. All three are often abandoned because they are hard to maintain.
• Intermittent fasting is another way to organise the same deficit. Its effect on weight is usually small and similar to other plans with the same deficit. In that review it remained a research question, without a recommendation [3]. At Alimmenta, we neither recommend nor prohibit it. If it leads you to reach dinner on an empty stomach and raid everything in sight, it is not for you. It is also unsuitable for minors, pregnant people or those who are breastfeeding. It is ruled out if you have or have had an eating disorder, or diabetes treated with insulin or medicines that can lower blood sugar too much.
• Diets that promise results by a deadline produce rapid weight loss, but what you lose is water and muscle. The catalogue of fad diets changes every year, and they all share three signs: they promise a date, cut out an entire food group and do not say what happens afterwards.

The same guideline is clear about restrictive and unbalanced diets: it advises against them because they do not work in the long term and can cause harm [3].

Do you need to count calories to lose weight?

You do not need to count them, but your intake does need to fall. To lose fat, you need to eat a little less than you expend, and that is a condition of any plan [3]. The plate described above, between three and five meals according to your day and your hunger, and less added fat can do that without an app or kitchen scales. Those changes last longer.

What is worth knowing is where the lower limit lies, because below it this stops being a matter of food and becomes treatment.

Do not go below 1,200 kilocalories a day on your own. The British obesity guideline calls a plan of 800 to 1,200 kcal a low-energy diet. It considers it only as part of a multicomponent programme with long-term follow-up, in a specialist service, nutritionally complete and for a limited time [3].

Below 800, even less so. This is a very-low-calorie diet and requires medical supervision within a programme involving several professionals [4]. It is reserved for people with an assessed clinical need to lose weight quickly [3], and neither approach is a long-term strategy [3].

At Alimmenta, we do not recommend diets of less than 1,200 kcal a day. Going below that amount requires medical supervision and can lead to nutrient deficiencies.

What changes depending on how much weight you want to lose

This is where the plan stops being the same for everyone. The plate stays the same; what changes is the timescale, what needs monitoring and who needs to oversee it.

• Five kilos. Often the last kilos, and the most stubborn. About ten weeks; you can find a full week’s menu in the guide to losing 5 kilos.
• Ten kilos. Four or five months. The challenge becomes keeping up the plan in August and at Christmas, as the guide to losing 10 kilos explains.
• Fifteen kilos. Seven or eight months at least, and often longer, because the pace slows as you lose weight. Here it is worth paying more attention to waist and hip measurements than to weight. The guide to losing 15 kilos explains it month by month.
• Twenty kilos or more. This is a long-term undertaking that is rarely done alone. The guide to losing 20 kilos explains how to divide it into stages.
• If you also eat a vegetarian or vegan diet, the plate keeps the same shape, but what goes in each section changes, as the guide to losing weight on a vegetarian diet explains.

If you have a considerable amount of weight to lose, the advice we always give is not to set your sights on the whole amount. Focus on the first three or four kilos. You reach the overall goal, and fewer people give up.

What should I eat for breakfast and dinner?

These are the two meals where plans tend to fall apart, for different reasons: breakfast because of time pressure, dinner because of tiredness.

At Alimmenta we recommend eating breakfast; having it matters more than the time you have it. What determines whether you lose weight is what you eat over the whole day. If you have breakfast, include protein and fruit or vegetables, rather than just refined carbohydrates. If breakfast does not agree with you or fit your lifestyle, do not force it. There are nine suggestions in nine breakfasts for weight loss.

First, let us clear up a myth about dinner. Eating dinner does not make you gain more weight simply because it is at night. Eating “just a salad” for dinner can leave you opening the fridge at eleven. Have vegetables, a simple protein and a small portion of carbohydrates. There are another nine dinner ideas for weight loss, all of which take less than fifteen minutes.

In consultations we often see dinner skipped because of poor planning, not feeling like cooking, a small appetite or getting home very late. What works is being aware of what makes it difficult and getting ahead of it. For example, when you make lunch, you can get dinner ready too.

Lunch tends to cause the fewest problems, because it is almost always decided in advance.

Do you need to exercise to lose weight?

You can lose weight without exercise. Exercise helps preserve muscle while you lose fat. The scales cannot distinguish between fat and lean mass: they show the same five-kilo loss in either case.

The Organización Mundial de la Salud recommends that adults aged 18 to 64 do 150 to 300 minutes of moderate activity each week [5]. That is twenty to forty minutes a day, and walking counts. It also recommends strength work for major muscle groups on two or more days [5].

For adults with obesity who want to lose fat while preserving lean mass, the specific recommendation is strength training two or three times a week [4]. It should be advised regardless of frequency and intensity because it helps maintain weight and improves body composition [4].

Preserving muscle helps maintain energy expenditure, which in turn helps prevent weight regain. You do not need a gym or equipment. Exercises using your own body weight (squats or wall push-ups) and the stairs at home can help you build strength and preserve muscle.

Why am I not losing weight? What we see in consultations

It is the question we hear most often, and the answer is almost never “because your metabolism is broken”. Here are the six reasons we see most often, in the order they tend to appear.

1. You eat too little and spread it poorly across the day. Hardly any breakfast, lunch on your feet, and by nine in the evening you arrive home hungry from the whole day. Or you skip a meal to make up for eating more earlier, which makes hunger build up even more. You can end up eating more this way. Aim for between three and five meals, depending on your day and your hunger.
2. You count what is on your plate but not what happens around it. What you snack on while cooking, oil poured without measuring, Friday’s beer, a piece of the children’s breakfast omelette. Simply notice it; you do not need to count it.
3. You have changed your meals, but your shopping is still the same. If the same foods keep coming into the house, the plan lasts only until the first difficult day.
4. You have cut food out of your plan to go faster. Out go the fruit, the yoghurt or the carbohydrates, or you fall short on protein. Your plan already has the deficit you need, and cutting it further leaves it too low in energy. Losing fat gets harder, hunger and cravings for certain foods increase, and it cannot be sustained. Skipping your fruit one day is no problem; the problem is when skipping it becomes a habit. Carbohydrates stay on the plate, in a smaller portion. Anything you cannot keep up in the long term takes you further from your goal, and it is what we repeat most in consultations.
5. You weigh yourself every day and read a normal change on the scales as a failure. Water, yesterday’s salt and the time of day can shift the reading by a kilo when nothing else has changed.
6. You have been doing this for three weeks. That is just the beginning. At half a kilo a week, there is little to see after three weeks, and it does not tell you much yet.

There is a seventh issue that a meal plan cannot fix: eating because of how you feel rather than because you are hungry. That calls for work with a psychologist before working on a menu. These six reasons, and a few more, are explained in the most common mistakes when you are not losing weight.

Why does the weight come back?

Because the plan usually ends while the circumstances that made it necessary remain. And because the environment does not help. The cheapest and most convenient food is often the most energy-dense, the car replaces walking, and advertising never stops.

The Canadian guidelines put it most honestly: they describe obesity as a chronic, complex disease with relapses [6]. Weight regain when treatment stops is to be expected with a condition like this, and says nothing about your willpower.

That is why the aim of treatment goes beyond weight loss and focuses on improving health [4]. Besides preserving muscle, two other things can help keep the weight off.

• Make the plan fit your life, including your schedule, the way you cook and your budget.
• Plan for the end of the plan from the beginning, rather than reaching a last day when you simply stop keeping track.

What about weight-loss pills and injections?

They exist and work for people for whom they are indicated, and a doctor is the person who assesses and prescribes them, after making a diagnosis. Some injections act on the GLP-1 receptor. We do not prescribe any of them, decide who needs them or advise against them.

Our work concerns what happens alongside treatment and afterwards: making sure the weight loss does not take muscle with it and that you are still eating enough during treatment, then helping you maintain habits that support your weight when treatment ends. If that is where you are, read about the rebound effect after stopping semaglutide (Ozempic, Wegovy).