Unintentional weight loss can occur because of an inadequately nutritious diet relative to a person's energy needs (generally called malnutrition). Disease processes, changes in metabolism, hormonal changes, medications or other treatments, disease- or treatment-related dietary changes, or reduced appetite associated with a disease or treatment can also cause unintentional weight loss.[25][26][27][31][32][33] Poor nutrient utilization can lead to weight loss, and can be caused by fistulae in the gastrointestinal tract, diarrhea, drug-nutrient interaction, enzyme depletion and muscle atrophy.[27] 

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The main advantage of the low-carb diet is that it causes you to want to eat less. Even without counting calories most overweight people eat far fewer calories on low carb. Sugar and starch may increase your hunger, while avoiding them may decrease your appetite to an adequate level. If your body wants to have an appropriate number of calories you don’t need to bother counting them. Thus: Calories count, but you don’t need to count them.
The Zone diet promotes eating a balance of each nutrient, without severely restricting calories. Protein increases your feeling of fullness, helping you to avoid eating between meals, and there is a guide to what kind of fat you can consume. Healthy fats are encouraged in place of the saturated and trans fats. The calorie restriction will help you lose weight.
For even more impressive effects on body composition: aim for exercise forms which elicit a positive hormonal response. This means lifting really heavy things (strength training), or interval training. Such exercise increases levels of the sex hormone testosterone (primarily in men) as well as growth hormone. Not only do greater levels of these hormones increase your muscle mass, but they also decrease your visceral fat (belly fat) in the long term. 

If you want to lose weight you should start by avoiding sugar and starch (like bread, pasta and potatoes). This is an old idea: For 150 years or more there have been a huge number of weight-loss diets based on eating fewer carbs. What’s new is that dozens of modern scientific studies have proven that, yes, low carb is the most effective way to lose weight.
This study took 83 subjects, estimated the daily calorie requirements of each person (aka their maintenance levels), and then created a caloric deficit of 30%. They then divided them up into 3 groups. The first had only 4% of their total daily calorie intake coming from carbs. The second had 50% of their total calorie intake coming from carbs. The third had 70% of their total calorie intake coming from carbs. Guess what happened? Even though some people were eating a VERY LOW carb diet and others were eating a VERY HIGH carb diet… they all lost the same amount of weight and body fat. Why? Because low carb or high carb isn’t what makes us gain or lose fat. Calories are, regardless of how many of them come from carbs.
The Core Plan is based on the science of energy density. Energy density refers to the amount of calories in a given weight of food. Foods that are considered low energy dense foods have a small amount of calories for a large volume of food (for example, vegetable soups, vegetables, and fruit). High energy dense foods provide a lot of calories for a small amount of food (for example, oils, butter, cream sauce). The Core Plan provides a "balanced diet by centering on a list of healthy foods that keep you full longer."
But just because belly fat comes off a bit more easily doesn’t make it less dangerous. In fact, it’s the exact opposite. “Belly fat is unfortunately the most dangerous location to store fat,” says Dr. Cheskin. Because belly fat—also known as visceral fat, or the deep abdominal fat that surrounds your organs—is more temporary, it’s more active in terms of circulating in the bloodstream. That means it’s likely to raise the amount of fat in your blood (known as blood lipid levels) and increase your blood sugar levels, which as a result raises your risk of heart disease and type 2 diabetes.

The key to losing weight is to burn more calories than you eat and drink. A diet can help you to do this through portion control. There are many different types of diets. Some, like the Mediterranean diet, describe a traditional way of eating from a specific region. Others, like the DASH eating plan or a diet to lower cholesterol, were designed for people who have certain health problems. But they may also help you to lose weight. There are also fad or crash diets that severely restrict calories or the types of food you are allowed to eat. They may sound promising, but they rarely lead to permanent weight loss. They also may not provide all of the nutrients your body needs.
Though not always followed for weight loss per se, an anti-inflammatory diet is rich in whole foods (including fresh fruits and veggies), and low in packaged, processed ones (like french fries and pastries), so there is a chance you will still shed pounds with this approach. But usually, folks follow this diet to help prevent or treat chronic diseases, such as multiple sclerosis, rheumatoid arthritis, Alzheimer’s, and cancer. And that’s smart, considering there’s a bounty of research to support this notion. Adopting this diet is relatively simple. It isn’t focused on counting calories or carbs, or following any sort of specific protocol. Instead of constantly thinking about the quantity of food you are eating, an anti-inflammatory is all about prioritizing the quality of what is on your plate.
Unsurprisingly, the results showed that nothing had happened to the weight of the women receiving calcium or the placebo. However, the group which took the multivitamin lost more weight – about 3 kg more – and improved their health markers. Among other things, their basal metabolic rate (the rate at which the body burns calories when at rest) increased.
When getting to grips with how to lose body fat there's plenty of food for thought. ‘Most women do perform better on a high protein, moderate fat and low carb diet,’ Vine says. ‘To maintain muscle, you typically need 0.5g protein per lb of body weight – this can be increased to 0.75g if you want to build more muscle (which will ultimately help to reduce body fat more quickly). For carbs, I suggest starting with 1g per pound of body weight then reducing down, if necessary, until it’s only fat coming off, not muscle.’

The conclusion? A caloric deficit is the sole cause of fat loss. Even if those calories come from the shittiest sources known to mankind, fat will STILL be lost. It’s not the source or the quality of those foods and the calories they provide… it’s the total quantity of it all. (Additional details here: Is Sugar Bad For You? How Much Should You Eat A Day?)

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