Calorie Deficit & Low-Calorie Diet: Complete Guide

Q: How do I create a calorie deficit diet plan?

Estimate your daily calorie needs with a TDEE calculator, then subtract 300–500 kcal (or more if advised by a professional) for a deficit. Build a low calorie diet plan around whole foods that fit that target. Use our calorie calculator and calorie deficit calculator to tailor the plan. A dietitian can help with a sustainable calorie deficit diet plan.

Last updated: 20 February 2026

A calorie deficit diet means eating fewer calories than your body burns each day so that you lose weight over time. A low calorie diet is one way to do that–often around 1,200–1,500 kcal per day for many adults, depending on size and activity, though your target should be based on your own TDEE and a safe deficit. This guide explains what a calorie deficit diet plan and low calorie diet plan are, how to set your target (including the role of a 1200 calorie diet, 1500 calorie diet, or 2000 calorie diet), what to eat to stay full and nourished, and why very low calorie diets (e.g. 800 calorie diet, 500 calorie diet) should only be used under medical supervision. Always discuss weight loss and calorie targets with your doctor or dietitian, especially if you have a health condition.

Disclaimer: This page is for education only and does not replace advice from your doctor or dietitian. Do not follow a very low calorie diet (e.g. 800 or 500 kcal per day) without medical approval. A safe calorie deficit depends on your size, activity, and health.

Below you will find how a calorie deficit diet works, how to build a calorie deficit diet plan or low calorie diet plan, what to eat and what to limit, risks of going too low (including 800 calorie diet, 1000 calorie diet, 500 calorie diet), a sample day, and answers to common questions. Use our calorie calculator, TDEE calculator, and calorie deficit calculator to set your target.

What is a calorie deficit diet?

A calorie deficit diet is any eating pattern where you consume fewer calories than your body uses (your total daily energy expenditure–TDEE). When you are in a deficit, the body draws on stored fat (and some muscle if the deficit is too large or protein is low) for energy, so you lose weight. There is no single “calorie deficit diet plan”–you set a daily calorie target below your TDEE and eat within it. A low calorie diet is simply one where that target is low relative to typical intake–often 1,200–1,800 kcal per day for adults, depending on size and activity. A 1200 calorie diet is common in popular plans but may be too low for taller or more active people; a 1500 calorie diet or 2000 calorie diet might suit others. Your calorie deficit diet plan should be based on your own TDEE minus a safe deficit (e.g. 300–500 kcal per day for about 0.5–1 kg loss per week).

Very low calorie diets–such as an 800 calorie diet, 1000 calorie diet, or 500 calorie diet–are sometimes used in medical programmes (e.g. for severe obesity under supervision, or in programmes like the Fast 800 diet or Dr Now diet / Dr Nowzaradan diet). These are not safe to do on your own; they can cause nutrient deficiencies, muscle loss, and other risks. This guide focuses on a sustainable low calorie diet plan and calorie deficit diet plan that you can tailor with our calculators and your doctor.

Core principles

Eat fewer calories than you burn (use TDEE calculator and calorie deficit calculator).
Aim for a modest deficit (e.g. 300–500 kcal per day) for steady, sustainable loss.
Choose nutrient-dense foods so you get enough protein, fibre, and vitamins on fewer calories.

How the calorie deficit and low-calorie diet work

Weight loss happens when energy in is less than energy out. Your TDEE is the calories you burn in a day; if you eat 300–500 kcal less than that, you are in a moderate deficit and typically lose about 0.5–1 kg (1–2 lb) per week. A low calorie diet achieves that by setting a daily target–e.g. a 1500 calorie diet for someone whose TDEE is 2,000. A 1200 calorie diet might be used by someone with a lower TDEE (e.g. smaller, sedentary) but can be too restrictive for many; never go below your BMR (basal metabolic rate) without medical advice. Use our BMR calculator and calorie deficit calculator to see a reasonable range.

There are no mandatory phases. You follow your calorie deficit diet plan or low calorie diet plan until you reach your goal, then adjust to maintenance (eating at TDEE). Programmes like the Fast 800 diet or 800 diet use a short period of very low calories (800 kcal) and are intended to be done with guidance; the Dr Now diet / Dr Nowzaradan diet plan is a very low calorie approach used in clinical settings. For most people, a sustained moderate deficit is safer and more sustainable than an 800 calorie diet or 500 calorie diet done alone.

What to eat and what to limit on a calorie deficit diet

On a calorie deficit diet or low calorie diet, every calorie counts–so focus on foods that are filling and nutritious. The table below summarises what to emphasise and what to limit so you can stick to your calorie deficit diet plan or low calorie diet plan without feeling deprived or missing nutrients.

Eat regularly (nutrient-dense, filling)	Eat in moderation	Limit or avoid
Vegetables (especially non-starchy, leafy greens)	Whole grains (oats, brown rice–watch portions)	Sugary drinks, sweets, pastries
Fruits (berries, apples, citrus)	Healthy fats (nuts, olive oil–calorie-dense)	Fried foods, highly processed snacks
Lean protein (chicken, fish, eggs, legumes)	Dairy (plain yogurt, cheese in moderation)	Large portions of calorie-dense meals
Legumes (beans, lentils, chickpeas)	Starchy vegetables (potatoes–portion control)	Alcohol (empty calories)

Protein and fibre help with fullness on a 1200 calorie diet, 1500 calorie diet, or any low calorie diet plan. Use our product calorie calculator and calorie table to check portions. Avoid crash diets or unplanned very low intake–a 500 calorie diet or 800 calorie diet without medical supervision is dangerous.

Potential benefits of a calorie deficit diet

When done in a sustainable way, a calorie deficit diet can support:

Weight loss: A consistent deficit leads to fat loss. A low calorie diet plan that you can maintain is more effective than a very aggressive plan you cannot stick to.
Metabolic health: Losing excess weight may improve blood sugar, cholesterol, and blood pressure in some people.

Quality of evidence: the role of calorie deficit in weight loss is well established. The key is setting a target that is safe and sustainable for you–use our calculators and, if needed, a dietitian.

Risks and who should be cautious

Going too low: A 500 calorie diet, 800 calorie diet, or even a 1000 calorie diet can cause fatigue, nutrient deficiencies, muscle loss, and gallstones if done without medical supervision. Very low calorie diets (VLCDs) are only for specific medical use with monitoring. Do not follow an 800 diet or Dr Now diet style plan on your own.

Who should be cautious: People with a history of eating disorders, pregnant or breastfeeding women, children, and anyone with a medical condition should set calorie targets with a doctor or dietitian. A 1200 calorie diet may be too low for taller or active people–your target should be based on your TDEE and a modest deficit, not a fixed number.

Before starting a calorie deficit diet plan or low calorie diet plan, especially if you have health conditions or plan to go below 1,200 kcal, consult your doctor or a registered dietitian.

Sample calorie deficit day (meal ideas)

This is one example of meals that could fit a low calorie diet (e.g. around 1,500 kcal)–not a prescriptive plan. Adjust portions to your target (use our calorie deficit calculator).

Breakfast: Oatmeal with fruit and a small handful of nuts; or eggs with vegetables and one slice of whole-grain toast; or Greek yogurt with berries.
Lunch: Large salad with grilled chicken or chickpeas and olive oil dressing; or vegetable soup with a whole-grain roll and an apple.
Dinner: Grilled fish or chicken with plenty of vegetables and a small portion of brown rice or quinoa; or a legume-based dish with vegetables.
Snacks: Fruit, raw vegetables, a small handful of nuts, or plain yogurt. Keep snacks moderate so you stay within your calorie deficit diet plan.

For a personalised calorie deficit diet plan or low calorie diet plan, use our calorie calculator, TDEE calculator, and calorie deficit calculator. For related approaches, see our weight loss diet and intermittent fasting diet guides.

Frequently asked questions about the calorie deficit and low-calorie diet

A calorie deficit diet means eating fewer calories than your body burns each day. Over time, your body uses stored fat for energy, so you lose weight. A safe deficit is often 300–500 kcal per day for about 0.5–1 kg (1–2 lb) loss per week. Use our TDEE calculator and calorie deficit calculator to set your target.

A low calorie diet typically means eating below your maintenance calories–often in the range of 1,200–1,500 kcal per day for many adults, depending on size and activity. A low calorie diet plan should be tailored to your TDEE and health. Very low calorie diets (e.g. 800 or 500 calorie diet) are only for specific medical use under supervision.

A 1200 calorie diet can be appropriate for some smaller, less active people but is too low for many others. It can risk nutrient gaps and fatigue. Your target should be based on your TDEE and a modest deficit (e.g. 300–500 kcal below TDEE). Use our calorie calculator and TDEE calculator and check with a doctor or dietitian.

Focus on nutrient-dense foods: vegetables, fruits, lean protein, whole grains, legumes, and healthy fats. They help you feel full and get enough vitamins and minerals while eating fewer calories. See the “What to eat and what to limit” section above for a table.

A very low calorie diet (VLCD) is usually 800 kcal or fewer per day (sometimes 500 calorie diet). It is used in some medical programmes (e.g. for severe obesity under supervision) and can cause nutrient deficiencies, muscle loss, and other risks. Do not follow an 800 calorie diet or 500 calorie diet without medical approval and monitoring.

Estimate your daily calorie needs with our TDEE calculator, then subtract 300–500 kcal (or more if advised by a professional) for a deficit. Build a low calorie diet plan around whole foods that fit that target. Use our calorie calculator and calorie deficit calculator. A dietitian can help with a sustainable calorie deficit diet plan.

Summary

A calorie deficit diet means eating fewer calories than you burn; a low calorie diet is one way to do that, often in the 1,200–1,500 kcal range for many adults. Set your target with our TDEE calculator and calorie deficit calculator–a 1200 calorie diet, 1500 calorie diet, or 2000 calorie diet may or may not suit you. Focus on nutrient-dense foods in your calorie deficit diet plan or low calorie diet plan. Do not follow an 800 calorie diet, 1000 calorie diet, or 500 calorie diet without medical supervision. Before starting, talk to your doctor or a dietitian. For related approaches, see our weight loss diet, intermittent fasting diet, and high-protein diet guides.