Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other connective tissue). Weight loss can either occur unintentionally because of malnourishment or an underlying disease, or from a conscious effort to improve an actual or perceived overweight or obese state. "Unexplained" weight loss that is not caused by a reduction in calorific intake or exercise is called cachexia and may be a symptom of a serious medical condition. Intentional weight loss is commonly referred to as slimming.

Types of Weight Loss:

Intentional: Intentional weight loss is the loss of total body mass as a result of efforts to improve fitness and health, or to change appearance through slimming. Weight loss is the main treatment for obesity, and there is substantial evidence this can prevent progression from prediabetes to type 2 diabetes with a 7-10% weight loss and manage cardiometabolic health for diabetic people with a 5-15% weight loss.

Unintentional: Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or a combination of these. It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months or 5% in the last month. Another criterion used for assessing weight that is too low is the body mass index (BMI). However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.

Tips to Lose Weight:

1. Protein addition to Your Diet:
When it comes to weight loss, protein is the king of nutrients. Your body burns calories when digesting and metabolizing the protein you eat, so a high-protein diet can boost metabolism by up to 80–100 calories per day. A high-protein diet can also make you feel more full and reduce your appetite. In fact, some studies show that people eat over 400 fewer calories per day on a high-protein diet. Even something as simple as eating a high-protein breakfast (like eggs) can have a powerful effect
2. Consume Whole, Single-Ingredient Foods:
One of the best things you can do to become healthier is to base your diet on whole, single-ingredient foods. By doing this, you eliminate the vast majority of added sugar, added fat, and processed food. Most whole foods are naturally very filling, making it a lot easier to keep within healthy calorie limits. Furthermore, eating whole foods also provides your body with the many essential nutrients that it needs to function properly. Weight loss often follows as a natural side effect of eating whole foods.
3. Processed Foods to be Avoided:
Processed foods are usually high in added sugars, added fats, and calories. What’s more, processed foods are engineered to make you eat as much as possible. They are much more likely to cause addictive-like eating than unprocessed foods
4. Healthy Foods and Snacks Stock Up:
Studies have shown that the food you keep at home greatly affects weight and eating behavior. By always having healthy food available, you reduce the chances of you or other family members eating unhealthy. There are also many healthy and natural snacks that are easy to prepare and take with you on the go. These include yogurt, whole fruit, nuts, carrots, and hard-boiled eggs.
5. Limit Your Intake of Added Sugar:
Eating a lot of added sugar is linked with some of the world’s leading diseases, including heart disease, type 2 diabetes, and cancer. On average, Americans eat about 15 teaspoons of added sugar each day. This amount is usually hidden in various processed foods, so you may be consuming a lot of sugar without even realizing it. Since sugar goes by many names in ingredient lists, it can be very difficult to figure out how much sugar a product actually contains. Minimizing your intake of added sugar is a great way to improve your diet.
6. Drink a Lot Of Water:
There is actually truth to the claim that drinking water can help with weight loss. Drinking 0.5 liters of water may increase the calories you burn by 24–30% for an hour afterward.  Drinking water before meals may also lead to reduced calorie intake, especially for middle-aged and older people. Water is particularly good for weight loss when it replaces other beverages that are high in calories and sugar
7. Drink Coffee (Unsweetened):
Fortunately, people are realizing that coffee is a healthy beverage that is loaded with antioxidants and other beneficial compounds. Coffee drinking may support weight loss by increasing energy levels and the number of calories you burn. Caffeinated coffee may boost your metabolism by 3–11% and reduce your risk of developing type 2 diabetes by a whopping 23–50%. Furthermore, black coffee is very weight loss friendly, since it can make you feel full but contains almost no calories.
8. Supplement With Glucomannan: 
Glucomannan is one of several weight loss pills that have been proven to work. This water-soluble, natural dietary fiber comes from the roots of the konjac plant, also known as the elephant yam. Glucomannan is low in calories, takes up space in the stomach, and delays stomach emptying. It also reduces the absorption of protein and fat, and feeds the beneficial gut bacteria. Its exceptional ability to absorb water is believed to be what makes it so effective for weight loss. One capsule is able to turn an entire glass of water into gel.
9. Avoid Liquid Calories:
Liquid calories come from beverages like sugary soft drinks, fruit juices, chocolate milk, and energy drinks. These drinks are bad for health in several ways, including an increased risk of obesity. One study showed a drastic 60% increase in the risk of obesity among children, for each daily serving of a sugar-sweetened beverage. It’s also important to note that your brain does not register liquid calories the same way it does solid calories, so you end up adding these calories on top of everything else that you eat.
10. Limit Your Intake of Refined Carbs:
Refined carbs are carbs that have had most of their beneficial nutrients and fiber removed. The refining process leaves nothing but easily digested carbs, which can increase the risk of overeating and disease. The main dietary sources of refined carbs are white flour, white bread, white rice, sodas, pastries, snacks, sweets, pasta, breakfast cereals, and added sugar.
11. Fast Intermittently:
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. There are a few different ways to do intermittent fasting, including the 5:2 diet, the 16:8 method, and the eat-stop-eat method. Generally, these methods make you eat fewer calories overall, without having to consciously restrict calories during the eating periods. This should lead to weight loss, as well as numerous other health benefits
12. Drink (Unsweetened) Green Tea:
Green tea is a natural beverage that is loaded with antioxidants. Drinking green tea is linked with many benefits, such as increased fat burning and weight loss. Green tea may increase energy expenditure by 4% and increase selective fat burning by up to 17%, especially harmful belly fat. Matcha green tea is a variety of powdered green tea that may have even more powerful health benefits than regular green tea.
13. Eat More Fruits and Vegetables:
Fruits and vegetables are extremely healthy, weight-loss-friendly foods. In addition to being high in water, nutrients, and fiber, they usually have very low energy density. This makes it possible to eat large servings without consuming too many calories. Numerous studies have shown that people who eat more fruits and vegetables tend to weigh less
14. Count Calories Once in a While:
Being aware of what you’re eating is very helpful when trying to lose weight. There are several effective ways to do this, including counting calories, keeping a food diary, or taking pictures of what you eat. Using an app or another electronic tool may be even more beneficial than writing in a food diary
15. Use Smaller Plates:
Some studies have shown that using smaller plates helps you eat less because it changes how you see portion sizes. People seem to fill their plates the same, regardless of plate size, so they end up putting more food on larger plates than smaller ones. Using smaller plates reduces how much food you eat while giving you the perception of having eaten more
16. Try a Low-Carb Diet:
Many studies have shown that low-carb diets are very effective for weight loss. Limiting carbs and eating more fat and protein reduces your appetite and helps you eat fewer calories. This can result in weight loss that is up to 3 times greater than that from a standard low-fat diet. A low-carb diet can also improve many risk factors for disease.
17. Eat More Slowly:
If you eat too fast, you may eat way too many calories before your body even realizes that you are full. Faster eaters are much more likely to become obese, compared to those who chewing more slowly may help you eat fewer calories and increase the production of hormones that are linked to weight loss
18. Replace Some Fat with Coconut Oil:
Coconut oil is high in fats called medium-chain triglycerides, which are metabolized differently than other fats. Studies show that they can boost your metabolism slightly while helping you eat fewer calories. Coconut oil may be especially helpful in reducing the harmful belly fat. Note that this does not mean that you should add this fat to your diet, but simply replace some of your other fat sources with coconut oil.
19. Add Eggs to Your Diet:
Eggs are the ultimate weight-loss food. They are cheap, low in calories, high in protein, and loaded with all sorts of nutrients. High-protein foods have been shown to reduce appetite and increase fullness, compared to foods that contain less protein. Furthermore, eating eggs for breakfast may cause up to 65% greater weight loss over 8 weeks, compared to eating bagels for breakfast. It may also help you eat fewer calories throughout the rest of the day
20. Spice Up Your Meals:
Chili peppers and jalapenos contain a compound called capsaicin, which may boost metabolism and increase the burning of fat. Capsaicin may also reduce appetite and calorie intake
21. Take Probiotics:
Probiotics are live bacteria that have health benefits when eaten. They can improve digestive health and heart health, and may even help with weight loss. Studies have shown that overweight and obese people tend to have different gut bacteria than normal-weight people, which may influence weight. Probiotics may help regulate healthy gut bacteria. They may also block the absorption of dietary fat while reducing appetite and inflammation. Of all the probiotic bacteria, Lactobacillus gasseri shows the most promising effects on weight loss
22. Get Enough Sleep:
Getting enough sleep is incredibly important for weight loss, as well as to prevent future weight gain. Studies have shown that sleep-deprived people are up to 55% more likely to become obese, compared to those who get enough sleep. This number is even higher for children. This is partly because sleep deprivation disrupts the daily fluctuations in appetite hormones, leading to poor appetite regulation
23. Eat More Fiber:
Fiber-rich foods may help with weight loss. Foods that contain water-soluble fiber may be especially helpful since this type of fiber can help increase the feeling of fullness. Fiber may delay stomach emptying, make the stomach expand, and promote the release of satiety hormones. Ultimately, this makes us eat less naturally, without having to think about it. Furthermore, many types of fiber can feed the friendly gut bacteria. Healthy gut bacteria have been linked with a reduced risk of obesity. Just make sure to increase your fiber intake gradually to avoid abdominal discomforts, such as bloating, cramps, and diarrhea.
24. Brush Your Teeth After Meals:
Many people brush or floss their teeth after eating, which may help limit the desire to snack or eat between meals. This is because many people do not feel like eating after brushing their teeth. Plus, it can make food taste bad. Therefore, if you brush or use mouthwash after eating, you may be less tempted to grab an unnecessary snack.
25. Combat Your Food Addiction:
Food addiction involves overpowering cravings and changes in your brain chemistry that make it harder to resist eating certain foods. This is a major cause of overeating for many people and affects a significant percentage of the population. In fact, a recent 2014 study found that almost 20% of people fulfilled the criteria for food addiction. Some foods are much more likely to cause symptoms of addiction than others. This includes highly processed junk foods that are high in sugar, fat, or both.
26. Do Some Sort of Cardio: 
Doing cardio — whether it is jogging, running, cycling, power walking, or hiking — is a great way to burn calories and improve both mental and physical health. Cardio has been shown to improve many risk factors for heart disease. It can also help reduce body weight. Cardio seems to be particularly effective at reducing the dangerous belly fat that builds up around your organs and causes metabolic disease
27. Add Resistance Exercises:
Loss of muscle mass is a common side effect of dieting. If you lose a lot of muscle, your body will start burning fewer calories than before. By lifting weights regularly, you’ll be able to prevent this loss in muscle mass. As an added benefit, you’ll also look and feel much better.
28. Use Whey Protein:
Most people get enough protein from diet alone. However, for those who don’t, taking a whey protein supplement is an effective way to boost protein intake. One study shows that replacing part of your calories with whey protein can cause significant weight loss, while also increasing lean muscle mass. Just make sure to read the ingredients list, because some varieties are loaded with added sugar and other unhealthy additives.
29. Practice Mindful Eating: 
Mindful eating is a method used to increase awareness while eating. It helps you make conscious food choices and develop an awareness of your hunger and satiety cues. It then helps you eat healthy in response to those cues. Mindful eating has been shown to have significant effects on weight, eating behavior, and stress in obese individuals. It is especially helpful against binge eating and emotional eating. By making conscious food choices, increasing your awareness, and listening to your body, weight loss should follow naturally and easily.
30. Focus on Changing Your Lifestyle:
Dieting is one of those things that almost always fails in the long term. In fact, people who “diet” tend to gain more weight over time. Instead of focusing only on losing weight, make it a primary goal to nourish your body with healthy food and nutrients.