Many different diet plans exist, each with its own approach to weight loss and health management. This article examines the three-phase FODMAP diet, popular diets like the South Beach Diet, and general principles applicable to any dietary change.
The Three-Phase FODMAP Diet
The three-phase fermentable oligo-, di-, mono-saccharides, and polyols (FODMAP) diet has demonstrated effectiveness in managing irritable bowel syndrome (IBS), largely due to education provided by dietitians. This dietetic process includes detailed assessment and follow-up throughout the restriction, re-introduction, and long-term maintenance stages.
Understanding FODMAPs
FODMAPs are short-chain carbohydrates present in various foods. They include monosaccharides and polyols, which are slowly absorbed in the small intestine, as well as di- and oligo-saccharides, which are indigestible due to the lack of suitable hydrolases or reduced hydrolase activity. The FODMAP diet traditionally involves initially restricting all FODMAPs to assess its effect on symptoms, and then developing a strategy for maintaining benefits over the long term with less restriction if a symptomatic response is achieved.
Implementing the FODMAP Diet
The initial consultation involves documenting the individual’s clinical issues using validated tools such as the Rome IV criteria, which measures symptom frequency and severity, and the Bristol stool form scale. The dietitian assesses the individual’s health and food knowledge, social environment, food preparation skills, personal responsibilities, and social systems that may influence their ability to adhere to dietary advice. Dietary intake is also assessed, noting FODMAP intake and potential triggers, possibly utilizing the Monash University Comprehensive Nutrition Assessment Questionnaire (CNAQ) or a 7-day food diary.
If the FODMAP diet is deemed appropriate, the dietitian educates the individual on normal gut physiology and the pathophysiology of disorders of gut-brain interaction (DGBI), including visceral hypersensitivity and altered bowel motility. They explain what FODMAPs are, their mechanisms of action, and food sources, providing information to implement the initial stage of the diet, including suitable low-FODMAP alternatives. Adjustments are made for existing dietary restrictions, such as vegetarianism, and uncontrolled environments, such as dining out.
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Following the restriction phase, a short-term follow-up assists the patient with implementing reintroduction. Clinical assessment at this stage involves measuring IBS symptoms and assessing adherence to dietary modifications. If there is inadequate symptom reduction, low adherence or ineffectiveness of the diet for the individual may be indicated. In such cases, implementation of the diet should cease, and other potential therapies should be explored. Regular short-term follow-ups may occur throughout the reintroduction phase to assist with implementation and address challenges with reintroduction, depending on the individual's requirements.
Personalization Phase
The personalization phase involves evaluating the impact of the FODMAP diet on the patient and tailoring a long-term diet that encourages nutritional adequacy and avoids the FODMAPs that trigger IBS symptoms for the individual. The patient should be encouraged to continue to reintroduce poorly tolerated high-FODMAP foods periodically to reassess tolerance, as tolerance may change over time. Education may also be centered around application of non-dietary DGBI therapies and how they may be combined with dietary therapy, such as peppermint oil, antispasmodic agents, and a-galactosidase, to reduce symptoms and allow more FODMAP flexibility in uncontrolled eating environments.
Nutritional and Psychological Risks
Strict long-term FODMAP avoidance may result in nutritional deficiency, as FODMAPs are naturally found in a large variety of commonly consumed foods. To reduce this risk, dietitians should encourage the substitution of high-FODMAP foods with nutritionally equivalent FODMAP alternatives, such as substituting cow’s milk with lactose-free cow’s milk or calcium-fortified soy protein milk.
The initial stage of the FODMAP diet is restrictive and may impact emotional and mental health. It is important to acknowledge the high risk of disordered eating behaviors in this patient group. Types of eating disorders that are thought to be associated with IBS are those linked to restrictive food choices rather than body dysmorphia, such as avoidant restrictive food intake disorder (ARFID) or orthorexia nervosa.
The South Beach Diet
The South Beach Diet, created by cardiologist Dr. Arthur Agatston, is a lower-carb diet designed to promote rapid weight loss without hunger while supporting heart health. It has three phases: two for weight loss and one for maintenance.
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How the South Beach Diet Works
Phase 1: Lasts 14 days and limits fruit, grains, and other higher-carb foods to decrease blood sugar and insulin levels, stabilize hunger, and reduce cravings. Most people can expect to lose 8-13 pounds during this phase. You consume three meals per day composed of lean protein, non-starchy vegetables, small amounts of healthy fat, and legumes, plus two mandatory snacks per day.
Phase 2: Begins on day 15 and continues until you reach your goal weight, with an average weight loss of 1-2 pounds per week. All foods from phase 1 are allowed, plus limited portions of fruit and “good carbs,” such as whole grains and certain types of alcohol.
Phase 3: Begins once you achieve your target weight. The phase-2 guidelines should be the basis for your lifestyle, but occasional treats are allowed. If you overindulge and start gaining weight, Dr. Agatston recommends returning to phase 1 for one to two weeks before returning to phase three.
Foods to Include and Avoid
Phase 1: Encourages monounsaturated oils such as olive, canola, macadamia, and avocado oils, as well as vegetable and seed oils like corn, flaxseed, grapeseed, peanut, safflower, sesame, and soybean oil. You may eat unlimited quantities of broth, herbs, spices, horseradish, mustard, lemon juice, salsa, all vinegars (with balsamic limited to 1 tbsp), light coconut milk (limited 1/4 cup), soy sauce, steak sauce, miso (limited to 1 1/2 tsp), coffee, tea, sugar-free sodas, and sugar-free drink mixes. Fatty meat, poultry, butter, coconut oil, whole milk, foods made with refined sugar, honey, maple syrup, agave nectar, grains, all fruits and fruit juice, beets, carrots, corn, turnips, yams, peas, white potatoes and winter squash, and alcohol are not allowed.
Phases 2 and 3: Gradually adds in higher-carb foods, beginning with one daily serving of fruit and whole grains or starchy vegetables for the first week. On the 14th day of phase 2 and thereafter, you may consume up to three servings of fruit and four servings of whole grains and starchy vegetables per day. An occasional alcoholic drink is also allowed, limited to light beer and dry wine. Fatty meat, poultry, butter, and coconut oil should be avoided, as well as whole milk, foods made with refined flour or sugar, honey, maple syrup, agave nectar, fruit juice, beets, corn and white potatoes, dates, figs, pineapple, raisins and watermelon, and alcohol other than light beer and dry wine.
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Benefits
The South Beach Diet may help you lose weight and belly fat, reduce insulin levels, increase hormone levels that promote fullness, and help protect heart health.
Drawbacks
The South Beach Diet may be overly restrictive concerning the amounts and types of fats allowed. It allows potentially harmful types of fat, such as soybean oil and safflower oil, which are extremely high in omega-6 fatty acids. In contrast, butter and coconut oil aren’t included on the South Beach Diet because they are high in saturated fat.
General Principles of Diet Plans
Calorie Deficit
A calorie deficit is stressful to the body physically, physiologically, and psychologically. During the deficit phase, the goal is to create a deficit, plan for weekly losses in fat, and track data points. The leaner an individual gets, the faster calories need to be reversed up.
Reverse Dieting
After a period of dieting, reverse dieting involves gradually increasing calorie intake to allow the metabolism to adjust and prevent weight regain. This process may take longer due to the initial and concluding phases but ultimately helps avoid weight regain post-diet.
Carbohydrate Management
The South Beach Diet limits some types of foods that have nutrients called carbohydrates. The South Beach Diet recommends that you limit simple carbs, such as candy or baked goods, over time and suggests that you choose complex carbs, such as whole grains, fruits, and vegetables.
What is a Low-FODMAP Diet?
FODMAP is an acronym for a certain class of carbohydrates, called fermentable short-chain carbohydrates, which are more difficult for people to digest. (The full acronym stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.) The low-FODMAP diet temporarily restricts these carbohydrates in order to relieve uncomfortable symptoms and give your digestive system a rest. Removing irritants gives your gut lining a chance to repair itself and can help restore a healthy balance of gut flora. If your symptoms improve, you can use the low-FODMAP diet to figure out which foods to limit in the future.
What are FODMAPs?
FODMAPs are:
- Fermentable. These are all foods that your gut bacteria feed on, converting them to gasses in a chemical process called fermentation.
- Oligosaccharides. These are soluble plant fibers known as prebiotics, which feed the beneficial bacteria in your gut. Oligosaccharides include onions, garlic, beans/lentils and many wheat products. Sensitivity to oligosaccharides may help explain some cases of non-celiac gluten sensitivity. Since gluten-free grains are lower in fermentable sugars than grains that have gluten, some people who think they are sensitive to gluten may actually be sensitive to the oligosaccharides residing in wheat products.
- Disaccharides. Lactose is the fermentable sugar in this group, the sugar in dairy and breast milk. Lactose intolerance is one of the most common food intolerances worldwide.
- Monosaccharides. Fructose, the sugar in fruit, is the fermentable sugar in this group. But only in certain quantities and proportions, so not all fruits are affected.
- Polyols. These are sugar alcohols, commonly used as artificial sweeteners. They are also found naturally in some fruits.
Why are FODMAPs difficult to digest?
FODMAPs are fermentable short-chain carbohydrates. Translated, that means two things: They are sugar molecules that are linked together in chains, and they are fermentable by the bacteria in your gut. Molecules in chains need to be broken down into single molecules to be absorbed through your small intestine. But FODMAPs can’t be broken down, so they can’t be absorbed there. Your small intestine draws in extra water to help move the FODMAPs through to your large intestine. There, the bacteria living in your colon have a field day fermenting them (eating them). This produces gasses and fatty acids as byproducts inside your gut.
Are FODMAPs bad for everyone?
Not at all. In fact, our digestive systems are designed to process some foods that we can’t fully digest ourselves - for example, dietary fiber, which has an important place in digestive health. And feeding the bacteria in our gut is part of our symbiotic arrangement with those bacteria. But some people with sensitive guts experience a level of indigestion from these foods that significantly impacts their quality of life. For these people, the byproducts of fermentation cause chronic symptoms of gas, bloating, abdominal pain and distension. The extra water drawn by the small intestine may cause diarrhea in excess, or constipation if there isn’t enough.
Who might benefit from a low-FODMAP diet plan?
The low-FODMAP diet is often prescribed for limited periods for people diagnosed with irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO). Studies show that a majority of people living with these conditions benefit from the diet. It can also be used as a short-term elimination diet for anyone who has digestive problems and wants to try and isolate the foods that are causing them. An elimination diet removes common problem foods and then adds them back in systematically to observe how your system reacts. The low-FODMAP diet is just one of many elimination diets that you can use to discover food sensitivities.
What does a low-FODMAP diet consist of?
The diet has three phases: an elimination phase, a reintroduction phase and a maintenance phase that’s customized to you. During the elimination phase, you'll avoid all of the high-FODMAP foods - a list of specific fruits, vegetables, dairy products and grains. At first glance, the elimination phase of the diet may seem very limited. But there’s still a good list of foods in each category that you can eat. It takes some mental discipline to follow, but you won’t go hungry on the diet. After two to four weeks, you’ll begin the reintroduction phase, in which you systematically add foods back in. The third phase keeps what works for you and leaves out what doesn’t.
What can I eat on the low-FODMAP diet?
Certain fruits, vegetables, grains and proteins are higher and lower in FODMAPs. Some are OK to eat in limited amounts but will bother you in larger amounts. For example, most legumes and processed meats are high in FODMAPs, but plain-cooked meats, tofu and eggs are low-FODMAP protein sources. Apples, watermelon and stone fruits are high in FODMAPs, but grapes, strawberries and pineapples are OK. A ripe banana is high in fructose, but you can have up to a third cut up in your cereal, or you can have a whole one if it’s not quite ripe. Your dietitian can help provide you with these kinds of specific guidelines for your diet.
Which high FODMAP foods are the best to avoid?
This is the question that you’ll need to answer for yourself during the process of the low-FODMAP diet. The answer will be different for everyone. The point of the diet is not to deprive you of “bad” foods but to find out if your symptoms are related to FODMAPs or not - and if they are, which ones. Some people may not improve at all on the elimination phase. If you don't, there’s no reason to follow through to the next phase. But if you do, it will be very important to reintroduce foods in a systematic way to separate the real offenders from foods that you can tolerate. Many people find in the end that it’s only one or two of the FODMAP food groups that bother them.