11 common weight-loss mistakes

Mistake 1: Starting with an unrealistic plan

It’s important to be realistic from the outset, and choose eating and exercise plans that you’ll be able to stick to for the long term. Consider how affordable your new diet will be and what time commitments will be required for food planning and cooking – how will these fit into your daily schedule of work and family life? Choose a plan that will be feasible in the long term, otherwise you may lose motivation.

Mistake 2: Being unaware of what and when you’re eating

Understanding the calorie content and nutritional composition of food and drink is essential in a weight-loss journey. You might be tempted to eat limitless fruit and veg, which is generally low-calorie and nutritious, but even these calories mount up over a day, so it’s best to track what you’re eating to be sure you’re within your allowance. Be mindful of snacking too – dried fruit in particular is energy-dense, so a little goes a long way. The easiest way to track your calorie intake is to use a nutrition app – this will help you understand exactly how much, as well as what and when, you're eating and drinking.

Mistake 3: Believing a calorie deficit is all that is needed

As science advances, we’re beginning to appreciate that the theory of calories in and calories out may be an oversimplification of how our body uses energy. Like most processes in the body, energy use and storage are all tightly controlled. This means the body strives to maintain a constant store of energy, so when it detects an energy shortfall it compensates by reducing the energy it uses, effectively slowing your metabolism. This maintains your energy stores at a fairly constant level.

A calorie deficit can be a helpful way to get your weight-loss journey started, but don’t expect it to solve your weight-loss issues. In the long term, this approach is not a sustainable way to lose weight and keep it off. Consistently restricting your calories is likely to leave you hungry, and if all you focus on are the calories on your plate, you may not be eating the well-balanced diet that will help secure your long-term health and fitness.

Mistake 4: Losing too much weight early on

Whatever weight-loss plan you follow, a general guide to aim for is a loss of about 1-2lb (0.5-1kg) per week. Some diets, such as the cabbage soup diet, claim to achieve quick results in the early weeks; however, nutritionists are quick to note that this weight is mostly water, and is easily regained once you resume a more balanced way of eating.

Severely restricting your calorie intake will also slow your metabolic rate, making weight loss more difficult in the longer term. The average requirements for moderately active adults are 2,500 kcals for men and 2,000 kcals for women each day, though be mindful that this is a rough guideline. To achieve sustainable weight loss, it's suggested you create a deficit of about 500 calories a day – this is considered to be enough to lose weight, yet maintain your metabolic rate.

Mistake 5: Not increasing activity levels

If you start to experience a weight-loss plateau yet are eating to a calorie deficit each day, consider your activity levels. Studies suggest that optimum weight-loss results are achieved when calorie restriction and activity are combined.

When it comes to which exercise is best, different types of exercise have different benefits: cardio can help burn calories, while resistance training builds muscle mass, which is associated with healthy weight in the long term. As a general guide, a good mix of cardio and resistance exercises each week will be a useful addition to any weight-loss plan. Studies suggest 225-420 minutes of physical activity per week is best to achieve weight loss, reducing to 200-300 minutes per week to simply keep the weight off.

Mistake 6: Eating lots of fat on a keto diet

If you choose to follow a keto plan and weight loss is your primary goal, be mindful that the excessive amounts of fat that can often be consumed in keto dishes will add calorie density and may impede your results. At 9kcal per gram, fat is more calorie-rich than either carbohydrates (4kcal/g) or protein (4kcal/g), so choose your foods wisely if you opt for a keto diet.

Mistake 7: Choosing the wrong foods

Specialist, calorie-counted diet foods may seem like a good choice, especially if you are watching calorie intake such as during the two ‘fasting’ days of the 5:2 diet, but they’re sometimes filled with ultra-processed ingredients, and often leave you feeling hungry. Similarly, reduced-fat or low-fat versions of foods aren’t always the healthiest options as food manufacturers sometimes replace fat with sugar.

Read food labels carefully, and consider the nutrient profile of your choices: a balance of high-fibre foods, lean proteins and fruit and veg can help guide you to long-term diet success and contribute to your overall health.

Mistake 8: Giving up when (inevitably) you hit a roadblock

Weight loss often isn't a straightforward, linear process, and life will often get in the way. When this happens, don't give up: it’s important to keep your end goal in sight and be kind to yourself in order to stay motivated. Look at your overall weight-loss journey – if you’re seeing a downward trend, you’re moving in the right direction. If you find yourself frequently slipping, the 80/20 rule diet, might be for you: this way of eating encourages followers to eat a healthy, balanced diet 80% of the time, and enjoy some of their favourite foods during the remaining 20%.

Mistake 9: Being a slave to the scales

Body weight can change quite a lot day-to-day due to changes in the amount of fluid you carry, therefore it’s important not to weigh yourself too often. The NHS recommends regular weekly to monthly intervals, at the same time of day, preferably in the morning. Or you could choose to skip the scales altogether and simply go on how you feel – do your clothes fit better? Do you have more energy? Are you sleeping better? How is your mood? These other measures of success can also help you to stay positive even if you’re not seeing results on the scales.

Mistake 10: Focusing too much on exercise and too little on what you eat

Diet plays a far more significant role in weight loss than exercise – some claim 70-80% – so what you eat really matters. Sadly, this also means exercise isn’t a free ticket to eat whatever you want; that cheeky treat at the end of a gym session could be undoing all your hard work! To achieve long-term weight loss and good overall health, a combination of a balanced diet and physical activity is key.

Mistake 11: Gaining weight as soon as you stop a weight-loss plan

An effective weight-loss plan will help instil behaviours and habits that you can take forward in your life to help you keep your weight in check. ‘Fad diets’ based on severe food restrictions often end in failure as they are unsustainable over the longer term and often don’t have a foundation in robust scientific evidence. For long-term success, look for diet plans and philosophies which encourage balanced eating, including all of the main food groups, and which consider the contribution nutrition plays in overall health, as well as healthy and steady weight loss.

Unfortunately, there is no single best strategy for weight loss and maintenance, and success will depend on you finding the best approach for your own circumstances and preferences.

Check with your GP before starting a weight-loss plan – this is especially relevant if you have a diagnosed medical condition, including diabetes, or a history of eating disorders.

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Exercise and weight loss:

How many calories will I burn?
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How many calories should I eat?
What is a calorie deficit?

This page was reviewed on 2 July 2024 by Kerry Torrens.

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