nutrition program services home

Weight Loss Methods for Adults

Separating the Good from the Bad

Fad and Popular Diets

What makes something a fad? The answer is: the way it is marketed. Any diet or nutritional practice that promises a quick fix is a fad. Any diet based on eating one food is a fad diet.  Any diet that is based on special supplements that can only be purchased from one particular company is a fad. Many fad diets do not offer anything new - they simply trick people into new ways of cutting calories.

While some popular diets are based on healthy nutrient intakes, many are not. The problem is that most people do not know how to tell which diets are healthy and effective and which are not. For credible weight loss information, see the websites in the resources section.

Reduced Fat, Reduced Carbohydrate or Reduced Protein Diets - Which Are Best

Calories in the diet come from three nutrients: carbohydrate, fat and protein. When any of these three nutrients are reduced, calories will be reduced. And any diet that reduces total calories will promote weight loss. So, for weight loss, it does not matter which nutrients are reduced or what kind of diet is followed, as long as the overall calories are reduced.

So, for weight loss, it does not matter which nutrients are reduced or what kind of diet is followed, as long as the overall calories are reduced. But for general health, how calories are reduced does matter. The National Institute of Medicine has defined ranges of carbohydrate, protein and fat intakes that are safe and healthy. These guidelines allow for a great deal of flexibility and individual variation. Diets that recommend intakes outside these ranges are unhealthy for most individuals. There are some exceptions. These are discussed in the following sections.

Reduced Fat Diets

Fat is an essential nutrient for health but it is also a very concentrated source of calories. Reducing fat in the diet is therefore an easy way to reduce calories and promote weight loss. But it is possible to reduce fat in the diet and not reduce calories. This can happen when people eat more carbohydrates or proteins to compensate for the reduction in fat, or buy reduced-fat foods and then eat larger portions of these foods. To lose weight on a reduced-fat diet, adults must avoid increasing their calorie intake in other ways.

How much fat should you eat? The National Institute of Medicine (NIM) recommends a range of 20 - 35% of total calories from fat for the general public. Weight loss experts experts recommend diets with no more than 20 - 30% of total calories from fat for people trying to lose weight. These are considered moderately low fat diets. To use a moderately low fat diet for weight loss, reduce the total number of calories to be eaten but make sure fat continues to provide 20 - 30% of the calories.  See Healthy Intakes of Carbohydrate, Fat and Protein and Help!! Is This a High Fat Food? for information on how to do this.

What about diets that have fat intakes outside this range?

These include the "Mediterranean" diet and the Ornish diet to reverse heart disease. Some versions of the Mediterranean diet have as many as 35 - 40% calories from fat while the Dean Ornish diet to reverse heart disease has a fat intake of 10% or less.

Are these diets healthy? The answer is yes - under some circumstances.

The Mediterranean diet is not one official diet: there are many versions and not all of them are healthy. The best Mediterranean diets include large amounts of low calorie, high fiber vegetables, and heart healthy fat mostly in the form of olive oil. Individuals wanting to follow a "Mediterranean" diet should make sure they are following a healthy version of the diet and are reducing total calories while following the diet. Consult a dietitian or physician for more information.

The Dean Ornish diet is a medically proven, effective diet to reverse heart disease. It also contains large amounts of low calorie, high fiber vegetables, but because fat intake is very low on this diet, medical and dietary supervision are required. Note that this diet is designed to reverse heart disease. It is not necessarily designed to promote weight loss. However, it can be used for weight loss if individuals reduce total calories while following it.

For people without heart disease, Dr. Ornish continues to recommend a low fat diet, with fewer than 20% of calories from fat. This is lower than the NIM recommended range. Some individuals do benefit from low fat diets but others may develop nutrient deficiencies if fat intake is too low. The decision to follow a low fat diet is best made on an individual basis and in consultation with a dietitian or physician.

To sum up: for weight loss, overall calories must be reduced. Reducing fat intake is one way to reduce calories, but individuals must be careful not to add the calories back into their diets in other ways.

For heart health and general health, calorie reduction should be done in a way that maintains a healthy proportion of fat in the diet. In general, weight loss experts recommend that weight loss diets contain 20 - 30 % of total calories from fat.

To convert fat percentages into grams of fat, see Healthy Intakes of Carbohydrate, Fat and Protein. For information about how to choose moderately low fat foods, see Help!! Is This a High Fat Food?. For information about the kinds of fats that should be in a diet for heart health (saturated, unsaturated, etc), see the American Heart Association's web site at

Reduced Carbohydrate Diets

Reduced carbohydrate diets seem to be effective diets for weight loss, but we do not know enough about their long term health effects. Although preliminary research indicates that weight loss can be safely accomplished on diets with as few as 35% of calories from carbohydrate, the NIM recommends not going below 45% of calories from carbohydrate. To convert carbohydrate percentages into grams, see Healthy Intakes of Carbohydrate, Fat and Protein.

The best known reduced carbohydrate diet is the Atkins® Diet. This diet is effective for short term weight loss but its long term effects on health are still unknown.

Very Low Calorie Diets (VLCD)

These are diets with fewer than 1200 calories per day. The most common VLCDs deliver 800 - 1000 calories per day. These diets are good choices for people who are very overweight, need extra help in losing weight, are willing to go on a monotonous diet and are willing to work closely with a physician or weight loss team.

In order to maintain health while following a VLCD, special formulas are used. The formulas contain protein and other nutrients that are necessary to preserve heart muscle and electrolytes during the dieting process. No one should go on a diet with fewer than 1200 calories per day without close supervision by a physician or a weight loss team.

The Glycemic Index and Weight Loss

The glycemic index (GI) measures how much a particular food raises blood sugar.  Although the GI concept first arose in the field of diabetes, it is sometimes used as a way to choose foods for weight loss. This is because many low glycemic foods are also low in calories and high in fiber. (Fiber helps people feel full sooner and eat less food.)

Low calorie, high fiber foods are excellent choices for healthy eating as well as for weight loss. However, selecting foods based only on the glycemic index is a misapplication of the index and likely to result in diet imbalances.

For example, some high glycemic foods become low glycemic foods when prepared in certain ways or when combined with other foods. Therefore, eliminating all foods with a high GI value is not necessary. Second, a few low glycemic foods have been mistakenly labeled as high glycemic foods. Carrots, for example, register high on the GI because of how they are prepared for GI testing. They are actually a low glycemic and low calorie food when eaten in normal portions.

Whole grains are usually recommended on the GI diet. They are high in fiber, but they are also high in calories. If they are eaten in large portions, overall calories may not be reduced and weight may not be lost. Fruits are often eliminated on the GI diet because they are high glycemic foods, but fruits are low calorie, high fiber foods when eaten in moderate portions. They also contain many important nutrients. Eliminating them entirely from the diet can cause vitamin deficiencies.

These points illustrate the complexity of nutrition concepts and the confusion that can arise when trying to follow popular advice about dieting. Adults should not eliminate so-called "high" glycemic foods from their diets or go on low glycemic diets without first consulting a dietitian or physician for more information.

Calcium and Weight Loss

A few studies have shown a small amount of weight loss when calcium intake was increased in overweight individuals whose diets were deficient in calcium.  Overweight individuals with normal dietary intakes of calcium experienced no weight loss benefit from increasing calcium intakes.  In fact, too much calcium in the diet can interfere with the absorption of other nutrients.  Adults, 19 - 50 years of age require 1000 mg. of calcium per day. Adults 51 - 70 years require 1200 mg. per day.

Commercial Meal Replacers

(Optifast®, Slim·Fast®, Nutrifast®, etc.)

Commercial meal replacer formulas are perfectly acceptable tools for weight loss when used appropriately.  These products are good for individuals who have difficulty regulating portion sizes.

Meal replacers usually contain 180 - 250 calories per container. Is one container a sufficient substitute for an entire meal? The answer depends on the total number of calories per day each individual needs.  Even when following a weight loss diet, many people need more than 180 - 250 calories per meal.  Other weight loss methods may not require people to know how many calories per day they should eat, but proper use of meal replacers does require this information. Therefore, anyone wanting to use meal replacers for weight loss should see a dietitian to find out how many calories per day and per meal they should be eating.

Many people use meal replacers to substitute for lunch. A much better choice would be to eat a regular (healthy) lunch and use the meal replacer to substitute for dinner. People who eat breakfast and lunch are less likely to overeat later in the day, and eating fewer calories at dinner is a very good strategy for weight loss.

Weight Loss Medications

FDA approved weight loss medications have been shown to be valuable tools for weight loss and for weight maintenance after weight loss. The medications can have side effects and cannot be taken by people with certain health conditions. However, they are excellent tools for people who can take the medications. Weight loss medications are appropriate for individuals whose BMIs* are over 30, or for individuals with BMIs between 27 - 29 who also have other weight-related problems (high blood pressure, high cholesterol, diabetes, etc). Consult your physician for more information.

* BMI = body mass index; a measure of body fatness.

Over-the-Counter Weight Loss Supplements and Herbs

Most over-the-counter weight loss products are ineffective.  The few that do work are amphetamines and substances similar to them (dexadrine, ephedra, etc.) These products promote weight loss by suppressing appetite, but they can also cause serious side effects such as high blood pressure, heart arrhythmias, and stroke.

Chromium is sometimes advertised as a weight loss aid. Chromium does play a role in nutrition, but it does not promote weight loss.  Other over-the-counter products such as hoodia, guar gum, chitosan, and guarana are equally ineffective in promoting weight loss. Further, because many of these substances are not regulated by the FDA, contents may vary (what is on the label may not necessarily be in the product), and some products may contain contaminants.

Bariatric Surgery

Bariatric surgery is a good choice for any individual ready to make serious and long lasting lifestyle changes. It is not a quick fix for weight loss. Weight can be regained after surgery if diet and lifestyle changes are not made. Portion sizes must be severely restricted after surgery. Liquids must be consumed separately from solids.  Some surgeries result in the lifelong need for specific vitamin supplementation.

In addition, all bariatric surgeries alter the digestive tract. Side effects such as dysphagia (difficulty swallowing), reflux, vomiting and kidney stones can occur. It is also possible to die from the surgery.

Weight can be regained after surgery if diet and lifestyle changes are not made. Therefore, bariatric surgery should not be taken lightly and is not a way to escape making dietary and lifestyle changes.


Healthy Intakes of Carbohydrate, Fat and Protein Translating Percents Into Grams

All healthy diets follow the National Institute of Medicine's (NIM) guidelines for carbohydrate, protein and fat intakes. Based on NIM guidelines, a healthy diet should contain:

  • 45 - 65% carbohydrate

  • 20 - 33% fat (for weight loss: 20 - 30% fat)

  • 10 - 35% protein

The chart below converts these percentages into grams. To use the chart, you need to know how many calories you should eat. For weight loss, a calorie intake between 1800-2200 calories is appropriate for many men, and a calorie intake between 1200 - 1800 calories is appropriate for many women.

The NIM's recommended range of intakes of carbohydrate, protein and fat is fairly broad. Do not be afraid to experiment with different intakes to find the ones that work best for you. For more information and assistance, consult a dietitian.

Total Daily Calories 1200 Calories 1500 Calories 1800 Calories 2000 Calories 2200 Calories 2500 Calories
20% calories from fat 27 g of fat 34 g 40 g 44 g 49 g 56 g
25% calories from fat 33 grams of fat 42 g 50 g 56 g 61 g 69 g
30% calories from fat 40 g of fat 50 g 60 g 67 g 73 g 83 g
33% calories from fat 44 g of fat 55 g 66 g 73 g 81 g 92 g
45% calories from carbs 135 g of carbs 169 g 203 g 225 g 248 g 281 g
50% calories from carbs 150 g of carbs 188 g 225 g 250 g 275 g 313 g
55% calories from carbs 165 g of carbs 206 g 248 g 275 g 303 g 344 g
60% calories from carbs 180 g of carbs 225 g 270 g 300 g 330 g 375 g
65% calories from carbs 195 g of carbs 244 g 293 g 325 g 358 g 406 g
10% calories from protein 30 g of protein 38 g 45 g 50 g 55 g 63 g
20% calories from protein 60 g of protein 75 g 90 g 100 g 110 g 125 g
30% calories from protein 90 g of protein 113 g 135 g 150 g 165 g 188 g
35% calories from protein 105 g of protein 131 g 158 g 175 g 193 g 219 g

Help!! Is This a High Fat Food???

Diets moderately low in fat are good diets to follow during and after weight loss.  These diets have no more than 5 grams of fat per serving or no more than 30% of calories from fat.

How do I know if a food has 30% of calories from fat?

  1. Look at the total calories per serving on the food label.
  2. Divide the total calories per serving by 3, in your head or with a calculator.
  4. This is your final number.
  5. Now look at the calories from fat per serving on the food label.
  6. If the calories from fat are more than your final number, it is a high fat food. Eat less of these foods.
  7. If the calories from fat are the same as your final number (or no more than 3 - 5 calories above or below), it is a moderately low fat food. Eat more of these foods.
  8. If the calories from fat are considerably less than your final number, it is a low fat food. Do include some low fat foods in your diet.


Information in this section was adapted from:


  • Adult Weight Management Evidence-Based Nutrition Practice Guideline, May 2006; American Dietetic Association Evidence Library;

  • " Role of the Primary Care Physician Before and After Weight Loss Surgery," Lisa Neff, MD, and Edward Saltzman, MD; Obesity Management, volume 1, no. 4, August 2005, 147-154.

  • "Managing Micronutrient Deficiencies in the Bariatric Surgery Patient," Robert Kushner, MD; Obesity Management, vol. 1, no. 5, October 2005, 203-206.

  • "Meal Replacement: A Valuable Tool for Weight Loss Management," Zhaoping Li, MD, Susan Bowerman, MD, and David Heber, MD, PhD;Obesity Management, vol. 2, no. 1, February, 2006, 23-30.

  • "Obesity Medications: Where Are We Headed?", Frank Greenway, MD and George Bray, MD; Obesity Management, vol. 2, no. 5, October, 2006, 181-185.

  • "Supplements Used in Weight Management", George Bray, MD and Donna Ryan, MD; Obesity Management, vol. 2, no. 5, October, 2006, 186-189.

  • "Intensive lifestyle changes for reversal of coronary heart disease." Five-year follow-up of the Lifestyle Heart trial, Ornish D, Scherwitz L, Billings J, et al. Journal of the American Medical Association. 1998; 280: 2001-2007.