Diet therapy, a biologically based practice, uses specialized dietary regimens (eg, Gerson therapy, macrobiotic diets, Pritikin diet) to
Treat or prevent a specific disorder (eg, cancer, cardiovascular disorders)
Generally promote wellness
Detoxify the body (ie, neutralize or eliminate toxins from the body)
Some diets (eg, Mediterranean diet) are widely accepted and encouraged in conventional and integrative medicine. Many other diets have been proposed as ways to promote health, with varying degrees of supportive evidence. They often make similar recommendations (eg, limiting less healthful fats and refined carbohydrates, substituting with plant-based and whole foods).
Diet therapy effects may occur slowly and are inherently difficult to study.
(See also Overview of Integrative, Complementary, and Alternative Medicine.)
Intermittent Fasting
Intermittent fasting has various forms, including restricting eating to certain times of the day (usually less than 10 hours, often called time-restricted feeding) or not eating for a day or longer (sometimes called alternate day fasting, for example). Intermittent fasting causes a switch from using glucose from the liver to ketones stored in fat (1). It has been shown to have favorable metabolic effects (eg, increased insulin sensitivity and autophagy, possibly increased life span) in animal studies. Human studies have shown health benefits, including reduced body weight and waist circumference, when compared to no dietary intervention; however, it is not clear whether long-term efficacy is proven (2) or is better than general caloric restriction (2, 3). One concern with weight loss is concurrent loss of lean body mass while losing fat mass (4); although loss of fat mass may contribute to metabolic benefits, this may be offset by the detrimental health effects of losing muscle mass (5).
Ornish Diet
This very low-fat vegetarian diet aims to help reverse arterial blockages that cause coronary artery disease and may help prevent or slow the progression of prostate and other cancers. It focuses on plant-based foods and avoidance of fat, refined carbohydrates, and animal protein. As a component of an intensive lifestyle program for participants with symptomatic coronary artery disease, the Ornish diet is effective and cost saving. However, it is not clear what benefits result from the specific food restrictions of the diet. Similar benefits may result from other diets that limit less healthful fats and refined carbohydrates but do not limit more healthful fats (eg, olive oil).
Macrobiotic Diet
This diet consists mainly of vegetables, whole grains, fruits, and cereals. Some proponents claim that this diet can prevent and treat cancer and other chronic disorders; however, no evidence supports efficacy of a macrobiotic diet for treatment of cancer. The macrobiotic diet has also been investigated in patients with metabolic syndrome, prediabetes, and diabetes without conclusive evidence of efficacy.
Risks of following this diet, other than lack of efficacy in disease prevention or therapy, are very few (6).
Paleo Diet
This diet consists of types of food allegedly consumed during the Paleolithic era, when food was hunted or gathered (ie, animals and wild plants). Thus, the diet includes
Increased protein intake
Decreased carbohydrate intake (with intake consisting mainly of nonstarchy fresh fruits and vegetables)
A moderate to higher fat intake (with intake mainly of monounsaturated and polyunsaturated fats)
Foods thought not to be available during the Paleolithic era (eg, dairy products, grains, legumes, processed oils, refined sugar, salt, coffee) are avoided. Proponents claim that human metabolism has not adapted to handle many of these foods.
Paleo diet is thought to treat or reduce the risk of coronary artery disease, metabolic syndrome, type 2 diabetes, and many chronic degenerative disorders (7, 8). The paleo diet also potentially promotes weight loss, improves athletic performance, enhances sleep, and improves mental function. However, there is limited evidence concerning the efficacy of this diet.
Risks include inadequate nutrition (due to decreased intake of whole grains and dairy).
Knowledge of what was eaten in the Paleolithic era is limited; however, some evidence suggests that the diet of the Paleolithic era was not as limited as the modern paleo diet.
References
1. de Cabo R, Mattson MP: Effects of intermittent fasting on health, aging, and disease [published correction appears in N Engl J Med. 2020 Jan 16;382(3):298] [published correction appears in N Engl J Med. 2020 Mar 5;382(10):978]. N Engl J Med 381(26):2541-2551, 2019. doi:10.1056/NEJMra1905136
2. Lowe DA, Wu N, Rohdin-Bibby L, et al: Effects of time-restricted eating on weight loss and other metabolic parameters in women and men with overweight and obesity: The TREAT randomized clinical trial [published correction appears in JAMA Intern Med. 2020 Nov 1;180(11):1555] [published correction appears in JAMA Intern Med. 2021 Jun 1;181(6):883]. JAMA Intern Med 180(11):1491-1499, 2020. doi:10.1001/jamainternmed.2020.4153
3. Gu L, Fu R, Hong J, Ni H, Yu K, Lou H: Effects of intermittent fasting in human compared to a non-intervention diet and caloric restriction: a meta-analysis of randomized controlled trials. Front Nutr 9:871682, 2022. Published 2022 May 2. doi:10.3389/fnut.2022.871682
4. Williamson E, Moore DR: A muscle-centric perspective on intermittent fasting: a suboptimal dietary strategy for supporting muscle protein remodeling and muscle mass? Front Nutr 8:640621, 2021. Published 2021 Jun 9. doi:10.3389/fnut.2021.640621
5. Srikanthan P, Karlamangla AS: Muscle mass index as a predictor of longevity in older adults. Am J Med 127(6):547-553, 2014. doi:10.1016/j.amjmed.2014.02.007
6. Harmon BE, Carter M, Hurley TG, et al: Nutrient composition and anti-inflammatory potential of a prescribed macrobiotic diet. Nutr Cancer. 67(6):933-40, 2015. doi: 10.1080/01635581.2015.1055369
7. Manheimer EW, van Zuuren EJ, Fedorowicz Z, et al: Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr102(4):922-32, 2015. doi: 10.3945/ajcn.115.113613
8. Whalen KA, Judd S, McCullough ML, et al: Paleolithic and Mediterranean diet pattern scores are inversely associated with all-cause and cause-specific mortality in adults. J Nutr 147(4):612-620, 2017. doi: 10.3945/jn.116.241919
