11 things you should consider before starting a diet

2. Is the weight loss plan scientifically sound?

This is one of the hardest questions to answer. Looking into the background and qualifications of the person behind the diet might give you some indication as to its legitimacy, but sometimes the answer isn’t clear cut. Even plans developed by trained medical professionals are not without their critics – Atkins was formulated by an American cardiologist, yet received a huge amount of criticism.

If you want guidance and reassurance that you're following a well-balanced plan, seek the help of a professional, such as a registered dietitian.

3. Is the weight loss plan safe?

Just because friends or family have had success with a particular diet doesn't mean it is right for you. 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.

Children, teenagers, the elderly and pregnant women have special nutritional requirements, and should not follow a restrictive eating plan unless they are under the supervision of a medical professional.

4. Does the diet provide enough calories?

As science advances, we’re beginning to appreciate that the theory of ‘calories in and calories out’ may be an oversimplification of the way our body uses energy. Like most processes in the body, energy use, expenditure and storage are tightly controlled. This means the body strives to maintain a constant store of energy, so when it detects a calorie shortfall it compensates by reducing the energy it uses, effectively slowing your metabolism. This maintains your energy stores at a fairly constant level and results in no more weight loss.

The best way to approach this is to understand your calorie needs. The average requirements for moderately active adults are 2,500 kcals for men and 2,000 kcals for women each day. When we go on a diet, we reduce our energy intake and create a calorie deficit – how you determine this figure is important because you need to eat enough calories to maintain your metabolic rate and continue your weight loss

A general guide is to aim for fat loss of about 1-2lb (0.5-1kg) per week. To achieve this, it's suggested you create a deficit of about 500 calories a day. The best 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.

Once you have this information, you can assess what your weight loss calorie needs are and identify where you might be able to reduce them.

5. Is the weight loss plan balanced?

Diets that encourage cutting out or severely restricting entire food groups or macronutrients, such as carbs, are likely to be unbalanced and difficult to stick to. Any diet that promotes eating mainly one type of food (such as the cabbage soup diet) may also put you at risk of nutritional deficiencies. These diets are short-term and do not offer a long-term solution for weight management.

Read our advice on eating a balanced diet.

6. Do the foods on the weight loss plan appeal to you?

Whatever your current diet, the foods and meal plans need to appeal and fit with your dietary preferences. If they don’t appeal, chances are you’ll seek out alternatives.

Another important factor is whether you prefer some flexibility in your food choices or are better suited to a prescriptive way of eating. The latter may be effective for the weight loss period but is less helpful as you navigate weight management.

7. Does the plan fit with your lifestyle and commitments?

If you’re usually short on time when it comes to shopping and cooking, a plan that involves lots of food preparation is not going to be right for you. Instead, look for one that offers quick-to-prepare solutions, or even a service that offers portion-controlled, ready-to-eat meals.

If you cook for others, it may be best to choose a plan that the whole family can follow – take a look at our healthy diet plans. Our recipes are designed so that they can be scaled up to accommodate more people.

8. Does the weight loss plan include support?

Many of us like the support of group meetings or online forums where we can ask questions and get extra encouragement when our commitment starts to waver. Being part of a group of like-minded people can also make the process more enjoyable.

9. Is the weight loss plan sustainable?

Maintaining a healthy weight and eating a balanced diet is something that you need to fit into your lifestyle permanently – if you revert back to your old eating habits, you're likely to put the weight back on. Can you make your chosen style of eating fit around your commitments? If you eat out or travel a lot for work, try to plan in advance how you might accommodate these scenarios – if the plan is too prescriptive you may find it hard to follow in the long term.

10. Does the plan promote physical activity?

If you start to experience a weight loss plateau, the key may lie in your activity levels. Studies suggest that optimum weight loss results are achieved when calorie restriction and activity are combined. Look for a weight loss plan that incorporates physical activity – this needn’t be in the form of structured classes, it could be as simple as adding a daily walk to your routine.

Find out more about walking and its many health benefits, as well as other cost-effective exercises.

11. Is the final goal realistic?

Some diets may lead to rapid weight loss in the short term, but the weight loss is rarely maintained once you resume a more balanced style of eating.

It's important to aim for an appropriate goal weight. You don't want to risk losing too much too soon or becoming underweight. The NHS offers an easy-to-understand tool to calculate your BMI – use this to work out your BMI and whether your target weight is healthy for you.

Discover our full range of popular diet guides including Atkins, keto and intermittent fasting, well as our nutritionist-approved healthy diet plans.

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This article was last reviewed on 9 November 2023 by Kerry Torrens.

Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last two decades she has been a contributing author to a number of nutritional and cookery publications including Good Food.

All health content on goodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.