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Anti-obesity medication or weight loss medications are pharmacological agents that reduce or control excess body fat. These medications alter one of the fundamental processes of the human body, weight regulation, by: reducing appetite and consequently energy intake, increasing energy expenditure, redirecting nutrients from adipose to lean tissue, or interfering with the absorption of calories. [1] [2] [3]
Weight loss drugs have been developed since the early twentieth century, and many have been banned or withdrawn from the market due to adverse effects, including deaths; other drugs proved ineffective. Although many earlier drugs were stimulants such as amphetamines, in the early 2020s, GLP-1 receptor agonists became popular for weight loss.
The medications liraglutide, [4] naltrexone/bupropion, [5] orlistat, [6] semaglutide, [7] and tirzepatide [8] are approved by the US Food and Drug Administration (FDA) for weight management in combination with reduced-calorie diet and increased physical activity. As of 2022, no medication has been shown to be as effective at long-term weight reduction as bariatric surgery. [9]
The first described attempts at producing weight loss are those of Soranus of Ephesus, a Greek physician, in the second century AD. He prescribed elixirs of laxatives and purgatives, as well as heat, massage, and exercise. This remained the mainstay of treatment for well over a thousand years. It was not until the 1920s and 1930s that new treatments began to appear. Based on its effectiveness for hypothyroidism, thyroid hormone became a popular treatment for obesity in euthyroid people. It had a modest effect but produced the symptoms of hyperthyroidism as a side effect, such as palpitations and difficulty sleeping. [36] 2,4-Dinitrophenol (DNP) was introduced in 1933; this worked by uncoupling the biological process of oxidative phosphorylation in mitochondria, causing them to produce heat instead of ATP. Overdose caused fatal hyperthermia and DNP also caused cataracts in some users. After the passage of the Food, Drug, and Cosmetic Act in 1938, the FDA banned DNP for human consumption. [37]
Amphetamines (marketed as Benzedrine) became popular for weight loss during the late 1930s. They worked primarily by suppressing appetite, and had other beneficial effects such as increased alertness. Use of amphetamines increased over the subsequent decades, including Obetrol and culminating in the "rainbow diet pill" regime. [38] This was a combination of multiple pills, all thought to help with weight loss, taken throughout the day. Typical regimens included stimulants, such as amphetamines, as well as thyroid hormone, diuretics, digitalis, laxatives, and often a barbiturate to suppress the side effects of the stimulants. [38] In 1967/1968 a number of deaths attributed to diet pills triggered a Senate investigation and the gradual implementation of greater restrictions on the market. [39] While rainbow diet pills were banned in the US in the late 1960s, they reappeared in South America and Europe in the 1980s. [38] In 1959, phentermine had been FDA approved and fenfluramine in 1973. In the early 1990s two studies found that a combination of the drugs was more effective than either on its own; fen-phen became popular in the United States and had more than 18 million prescriptions in 1996. [40] Evidence mounted that the combination could cause valvular heart disease in up to 30 percent of those who had taken it, leading to withdrawal of fen-phen and dexfenfluramine from the market in September 1997. [39]
In the early 2020s, GLP-1 receptor agonists such as semaglutide or tirzepatide became popular for weight loss because they are more effective than earlier drugs, causing a shortage for patients prescribed these medications for type 2 diabetes, their original indication. [41] [42]
After the FDA approved semaglutide (Wegovy®) [43] and tirzepatide (Zepbound®) [44] for chronic weight management, GLP-1 medications became available through various virtual weight loss programs, one of which being LifeMD.
The United States Food and Drug Administration and the European Medicines Agency have approved weight loss medications for adults with either a body-mass index (BMI) of at least 30, or a body-mass index of at least 27 with at least one weight-related comorbidity. This patient population is considered to have sufficiently high baseline health risks to justify the use of anti-obesity medication. [45] [46]
The American Academy of Pediatrics had not previously supported the use of weight loss medication in adolescents but issued new guidelines in 2023. It now recommends considering the use of weight loss medication in some overweight children aged 12 or older. [47] The European Medicines Agency has approved semaglutide for children aged 12 or older who have a BMI in the 95 percentile for their age and a weight of at least 60 kilograms (130 lb). [48] [46] However, GLP-1 agonists may not be cost effective in this population. [49]
The US Food and Drug Administration (FDA) approves anti-obesity medications as an adjunctive therapy to diet and exercise for people for whom lifestyle changes do not result in sufficient weight loss. In the United States, semaglutide (Wegovy) is approved by the FDA for chronic weight management. [50] The FDA guidelines say that a therapy may be approved if it results in weight loss that is statistically significant greater than placebo and generally at least five percent of body weight over six months that comes predominantly from fat mass. [18] [51] Some other prescription weight loss medications are stimulants, which are recommended only for short-term use, and thus are of limited usefulness for patients who may need to reduce weight over months or years. [52] As of 2022, there is no pathway for approval for drugs that reduce fat mass without 5 percent overall weight loss, even if they significantly improve metabolic health; neither is there one for drugs that help patients maintain weight loss although this can be more challenging than losing weight. [18]
As of 2022, no medication has been discovered that would equal the effectiveness of bariatric surgery for long-term weight loss and improved health outcomes. [9]
Medication Name | Trade name(s) | Mechanism of action | Current FDA Status | placebo-adjusted percent bodyweight lost (highest dose studied) |
---|---|---|---|---|
Semaglutide | Wegovy, Ozempic | GLP-1 receptor agonist | Approved for weight management (chronic) | 12% [53] |
Phentermine/topiramate | Qsymia | Phentermine is a substituted amphetamine and topiramate has an unknown mechanism of action | Approved for weight management (short-term) by the FDA but not the European Medicines Agency [54] | 10% [55] or 8.25 kilograms (18.2 lb) [56] |
Naltrexone/bupropion | Contrave | Approved for weight management (chronic) in the US and EU [57] | 5 percent [17] | |
Liraglutide | Saxenda | GLP-1 receptor agonist | Approved for weight management (chronic) | 4 percent [58] |
Gelesis100 | Plenity | Oral hydrogel | FDA approved for weight management (chronic) but the American Gastroenterology Association recommends that its use be limited to clinical trials due to lack of evidence. [59] | 2% [60] |
Orlistat | Xenical | Absorption inhibitor | Approved for weight management (chronic) | 3 kilograms (6.6 lb); percentage not provided [61] |
Phentermine | Substituted amphetamine | Approved for weight management (short-term) | 5 kilograms (11 lb) [62] | |
Methamphetamine | Desoxyn | Substituted amphetamine | Approved for weight management (short-term) | |
Tirzepatide | Zepbound | Dual GLP-1 receptor agonist and GIP agonist | FDA approved for weight management (chronic); [63] EMA approval for weight loss is pending [64] | 10.91 kilograms (24.1 lb) [65] |
Medication Name | Trade name(s) | Mechanism of action | Current FDA Status | placebo-adjusted percent bodyweight lost (highest dose studied) |
---|---|---|---|---|
Lorcaserin | Belviq | 5-HT2C receptor agonist | Withdrawn for safety reasons | 6.25 percent [66] |
Sibutramine | Meridia | Serotonin–norepinephrine reuptake inhibitor | Withdrawn due to cardiovascular risks [67] [68] | 19.7 percent [69] |
Rimonabant | Acomplia, Zimbutli | Cannabinoid receptor antagonist | Withdrawn for safety reasons | 2.6 to 6.3 kilograms (5.7 to 13.9 lb) [70] |
Fenfluramine | Fintepla, Pondimin | Serotonin releasing agent | Withdrawn for safety reasons | - |
Fenfluramine/phentermine (fen-phen) | Pondimin | Withdrawn for safety reasons | 13.9 percent [71] | |
Dexfenfluramine | Redux | Serotonin releasing agent | Withdrawn for safety reasons | 3.5 kilograms (7.7 lb) [72] |
2,4-Dinitrophenol | Uncoupling agent | Withdrawn for safety reasons | 17.1 pounds (7.8 kg) per patient on average (uncontrolled study) [73] | |
Ephedrine | Adrenergic agonist | Approved for asthma [74] | Average of 1.9 kilograms (4.2 lb) in a meta-analysis (all dosages) [75] | |
ECA stack | Combination of ephedrine and caffeine, sometimes adding aspirin | Around 4–6 kilograms (8.8–13.2 lb) [76] | ||
Ephedra | Plant extract sold as a dietary supplement | Contains ephedrine, an adrenergic agonist | Banned in 2004 for safety reasons | 0.9 kilograms (2.0 lb) per month more than placebo [76] |
Amphetamine salts | Obetrol | Approved 1960, withdrawn 1973; Adderall was later approved for ADHD and narcolepsy and is still used for those purposes | ||
Phenylpropanolamine | Was an over-the-counter medication ingredient | Withdrawn in 2005 due to risk of hemorragic stroke | 1.5 kilograms (3.3 lb) [77] |
Medication Name | Trade name(s) | Mechanism of action | Current FDA Status | placebo-adjusted percent bodyweight lost (highest dose studied) |
---|---|---|---|---|
Retatrutide | GLP-1, GIP, and glucagon receptor triple agonist | In clinical trials | 24 percent in a Phase II trial [78] | |
Exenatide | Byetta | GLP-1 receptor agonist | Approved for type 2 diabetes | 2.5 kilograms (5.5 lb) [79] |
Cetilistat | Absorption inhibitor | Not approved | 1.5 kilograms (3.3 lb) [80] | |
Tesofensine (NS2330) | Serotonin–norepinephrine–dopamine reuptake inhibitor | Not FDA approved | 10.6 percent [81] | |
Metformin | Glucophage | Unknown | Approved for type 2 diabetes | 5.6 percent [82] |
Cagrilintide | Dual amylin and calcitonin receptor agonist (DACRA) | Not approved | 7.8 percent [83] | |
Cagrilintide/semaglutide | CagriSema | DACRA/GLP-1 agonist combination | Not approved | 15.4 percent after 32 weeks [27] |
Some anti-obesity medications can have severe, even, lethal side effects, fen-phen being a famous example. Fen-phen was reported through the FDA to cause abnormal echocardiograms, heart valve problems, and rare valvular diseases. [84] Out of 25 anti-obesity medications withdrawn from the market between 1964 and 2009, 23 acted by altering the functions of chemical neurotransmitters in the brain. The most common side effects of these drugs that led to withdrawals were mental disturbances, cardiac side effects, and drug abuse or drug dependence. Deaths were associated with seven products. [85] Ephedra was removed from the US market in 2004 over concerns that it raises blood pressure and could lead to strokes and death. [86]
Drugs used in diabetes treat diabetes mellitus by decreasing glucose levels in the blood. With the exception of insulin, most GLP-1 receptor agonists, and pramlintide, all diabetes medications are administered orally and are thus called oral hypoglycemic agents or oral antihyperglycemic agents. There are different classes of hypoglycemic drugs, and selection of the appropriate agent depends on the nature of diabetes, age, and situation of the person, as well as other patient factors.
Orlistat, sold under the brand name Xenical among others, is a medication used to treat obesity. Its primary function is preventing the absorption of fats from the human diet by acting as a lipase inhibitor, thereby reducing caloric intake. It is intended for use in conjunction with a healthcare provider-supervised reduced-calorie diet.
Incretins are a group of metabolic hormones that stimulate a decrease in blood glucose levels. Incretins are released after eating and augment the secretion of insulin released from pancreatic beta cells of the islets of Langerhans by a blood-glucose–dependent mechanism.
Exenatide, sold under the brand name Byetta among others, is a medication used to treat type 2 diabetes. It is used together with diet, exercise, and potentially other antidiabetic medication. It is a treatment option after metformin and sulfonylureas. It is given by injection under the skin.
Glucagon-like peptide-1 (GLP-1) is a 30- or 31-amino-acid-long peptide hormone deriving from the tissue-specific posttranslational processing of the proglucagon peptide. It is produced and secreted by intestinal enteroendocrine L-cells and certain neurons within the nucleus of the solitary tract in the brainstem upon food consumption. The initial product GLP-1 (1–37) is susceptible to amidation and proteolytic cleavage, which gives rise to the two truncated and equipotent biologically active forms, GLP-1 (7–36) amide and GLP-1 (7–37). Active GLP-1 protein secondary structure includes two α-helices from amino acid position 13–20 and 24–35 separated by a linker region.
The glucagon-like peptide-1 receptor (GLP1R) is a G protein-coupled receptor (GPCR) found on beta cells of the pancreas and on neurons of the brain. It is involved in the control of blood sugar level by enhancing insulin secretion. In humans it is synthesised by the gene GLP1R, which is present on chromosome 6. It is a member of the glucagon receptor family of GPCRs. GLP1R is composed of two domains, one extracellular (ECD) that binds the C-terminal helix of GLP-1, and one transmembrane (TMD) domain that binds the N-terminal region of GLP-1. In the TMD domain there is a fulcrum of polar residues that regulates the biased signaling of the receptor while the transmembrane helical boundaries and extracellular surface are a trigger for biased agonism.
Liraglutide, sold under the brand name Victoza among others, is an anti-diabetic medication used to treat type 2 diabetes, and chronic obesity. It is a second-line therapy for diabetes following first-line therapy with metformin. Its effects on long-term health outcomes like heart disease and life expectancy are unclear. It is given by injection under the skin.
Lorcaserin, marketed under the brand name Belviq, was a weight-loss drug developed by Arena Pharmaceuticals. It reduces appetite by activating serotonin receptor the 5-HT2C receptor in the hypothalamus, a region of the brain which is known to control appetite. It was approved in 2012, and in 2020, it was removed from the market in the United States due to an increased risk of cancer detected in users of Belviq.
Glucagon-like peptide-1 (GLP-1) receptor agonists, also known as GLP-1 analogs, GLP-1DAs or incretin mimetics, are a class of anorectic drugs that reduce blood sugar and energy intake by activating the GLP-1 receptor. They mimic the actions of the endogenous incretin hormone GLP-1 that is released by the gut after eating.
Management of obesity can include lifestyle changes, medications, or surgery. Although many studies have sought effective interventions, there is currently no evidence-based, well-defined, and efficient intervention to prevent obesity.
Dulaglutide, sold under the brand name Trulicity among others, is a medication used for the treatment of type 2 diabetes in combination with diet and exercise. It is also approved in the United States for the reduction of major adverse cardiovascular events in adults with type 2 diabetes who have established cardiovascular disease or multiple cardiovascular risk factors.
Setmelanotide, sold under the brand name Imcivree, is a medication used for the treatment of genetic obesity caused by a rare single-gene mutation.
Semaglutide is an antidiabetic medication used for the treatment of type 2 diabetes and an anti-obesity medication used for long-term weight management. It is a peptide similar to the hormone glucagon-like peptide-1 (GLP-1), modified with a side chain. It can be administered by subcutaneous injection or taken orally. It is sold under the brand names Ozempic and Rybelsus for diabetes, and under the brand name Wegovy for weight loss.
Tirzepatide is an antidiabetic medication used for the treatment of type 2 diabetes and for weight loss. Tirzepatide is administered via subcutaneous injections. It is sold under the brand names Mounjaro for diabetes treatment, and Zepbound for weight loss.
Cagrilintide/semaglutide, marketed as CagriSema, is a combination of cagrilintide, a dual amylin and calcitonin receptor agonist, and semaglutide, a GLP-1 agonist. It is injected once weekly and is being tested in type 2 diabetes and obesity. Preliminary trial results found a greater weight loss compared to either medication alone. HbA1c was significantly improved compared to cagrilintide alone and non-significantly better than semaglutide alone. In a Phase II trial, weight loss averaged -15.6 percent after 32 weeks, making CagriSema comparable in efficacy to tirzepatide. A future trial sponsored by Novo Nordisk is comparing tirzepatide and CagriSema head-to-head. As of 2023, CagriSema is in a Phase III trial.
NNC9204-1706 or NN9423 is a GLP-1/GIP/glucagon receptor triple agonist developed by Novo Nordisk. It was evaluated in a clinical trial; adverse effects such as "dose-dependent increases in heart rate and reductions in reticulocyte count, increases in markers of inflammation and hepatic disturbances, and impaired glucose tolerance at the highest dosages" meant that the drug was declared to have an inadequate safety profile and discontinued.
Glucagon receptor agonists are a class of drugs under development for the treatment of obesity, non-alcoholic fatty liver disease, and congenital hyperinsulinism.
GLP1 poly-agonist peptides are a class of drugs that activate multiple peptide hormone receptors including the glucagon-like peptide-1 (GLP-1) receptor. These drugs are developed for the same indications as GLP-1 receptor agonists—especially obesity, type 2 diabetes, and non-alcoholic fatty liver disease. They are expected to provide superior efficacy with fewer adverse effects compared to GLP-1 mono-agonists, which are dose-limited by gastrointestinal disturbances. The effectiveness of multi-receptor agonists could possibly equal or exceed that of bariatric surgery. The first such drug to receive approval is tirzepatide, a dual agonist of GLP-1 and GIP receptors.
VK2735 is a dual agonist of the GLP-1 receptor and GIP receptor, with a similar mechanism of action as tirzepatide, which acts on the same receptors. It is injectable and is being developed by Viking Therapeutics.
Lotte Bjerre Knudsen is a Danish scientist and university professor. She led the development of liraglutide and oversaw the development of semaglutide, two notable drugs approved for indications in the treatment of diabetes and obesity.
Over all, meta-analysis showed a significant reduction in body weight in the tirzepatide group versus the placebo group by -9.81 kg (95% CI (-12.09, -7.52). There were three doses investigated compared to the placebo group were affected significantly reduced the body weight of patients [5 mg: MD = -7.52 kg, 95% CI (-10.86, -4.18), P < 0.0001; I2 = 94%; 10 mg: MD = -10.48 kg, 95% CI (-15.34, -5.62), P < 0.0001; I2 = 97%; 15 mg: MD = -10.91 kg, 95% CI (-14.81, -7.01), P < 0.00001; I2 = 96%]