Compared with usual diet, moderate certainty evidence supports modest weight loss and substantial reductions in systolic and diastolic blood pressure for low carbohydrate (eg, Atkins, Zone), low fat (eg, Ornish), and moderate macronutrient (eg, DASH, Mediterranean) diets at six but not 12 months. Differences between diets are, however, generally trivial to small, implying that people can choose the diet they prefer from among many of the available diets (fig 6) without concern about the magnitude of benefits.
The worldwide prevalence of obesity nearly tripled between 1975 and 2018.1 In response, authorities have made dietary recommendations for weight management and cardiovascular risk reduction.23 Diet programmes—some focusing on carbohydrate reduction and others on fat reduction—have been promoted widely by the media and have generated intense debates about their relative merit. Millions of people are trying to lose weight by changing their diet. Thus establishing the effect of dietary macronutrient patterns (carbohydrate reduction v fat reduction v moderate macronutrients) and popular named dietary programmes is important.
Biological and physiological mechanisms have been proposed to explain why some dietary macronutrient patterns and popular dietary programmes should be better than others. A previous network meta-analysis, however, suggested that differences in weight loss between dietary patterns and individual popular named dietary programmes are small and unlikely to be important.4 No systematic review and network meta-analysis has examined the comparative effectiveness of popular dietary programmes for reducing risk factors for cardiovascular disease, an area of continuing controversy.
Nathan Pritikin was a college dropout who became an entrepreneur. While doing research for the government during World War II, he observed that populations that had extremely limited food availability because of the war had substantially reduced mortality from cardiovascular disease—something unexpected at a time when cardiovascular disease was thought to be due to stress.
After the war when food became more available CVD death rates went back up, resulting in Pritikin concluding that CVD was related to diet. Pritikin devised his own very low-fat diet that bears his name and the diet is still in use 65 years later.
Habitual fish oil supplementation is associated with a 13% lower risk of all cause mortality, a 16% lower risk of CVD mortality, and a 7% lower risk of CVD events among the general population
Fish oil is a rich source of long chain omega 3 fatty acids, a group of polyunsaturated fats that primarily include eicosapentaenoic acid and docosahexaenoic acid. Initially, these compounds were recommended for daily omega 3 fatty acid supplementation for the prevention of cardiovascular disease (CVD). Consequently, the use of fish oil supplements is widespread in the United Kingdom and other developed countries.
Several mechanisms could explain the benefits for clinical outcome derived from fish oil supplementation. Firstly, the results of several studies have indicated that supplementation with omega 3 fatty acids has beneficial effects on blood pressure, plasma triglycerides, and heart rate, all of which would exert a protective effect against the development of CVD. Secondly, several trials have shown that omega 3 fatty acids can improve flow mediated arterial dilatation, which is a measure of endothelial function and health. Thirdly, omega 3 fatty acids have been shown to possess antiarrhythmic properties that could be clinically beneficial. Finally, studies have reported that fish oil can reduce thrombosis. Additionally, studies have reported that the anti-inflammatory properties of fish oil could have a preventive role in the pathophysiology of CVD outcomes. Other mechanisms could also be involved to explain the effect of fish oil on CVD outcomes.
From a New York Times article by Jane E. Brody (Feb 17, 2020):
“It takes 10 to 12 hours to use up the calories in the liver before a metabolic shift occurs to using stored fat,” Dr. Mattson told me. After meals, glucose is used for energy and fat is stored in fat tissue, but during fasts, once glucose is depleted, fat is broken down and used for energy.
I was skeptical, but it turns out there is something to be said for practicing a rather prolonged diurnal fast, preferably one lasting at least 16 hours. Mark P. Mattson, neuroscientist at the National Institute on Aging and Johns Hopkins University School of Medicine, explained that the liver stores glucose, which the body uses preferentially for energy before it turns to burning body fat.
For example, human studies of intermittent fasting found that it improved such disease indicators as insulin resistance, blood fat abnormalities, high blood pressure and inflammation, even independently of weight loss. In patients with multiple sclerosis, intermittent fasting reduced symptoms in just two months, a research team in Baltimore reported in 2018.
On the Mayo Clinic Radio program, Dr. Donald Hensrud, director of the Mayo Clinic Healthy Living Program, discusses the obesity epidemic and talks about popular diet trends, including intermittent fasting.
…It seems fasting triggers a dramatic switch in the body’s metabolism, according to a paper Mattson and colleagues published in February in the experimental biology journal FASEB. In humans, fasting for 12 hours or more drops the levels of glycogen, a form of cellular glucose. Like changing to a backup gas tank, the body switches from glucose to fatty acids, a more efficient fuel. The switch generates the production of ketones, which are energy molecules that are made in the liver. “When the fats are mobilized and used to produce ketones, we think that is a key factor in accruing the health benefits,” says Mattson.