Varady KA, Roohk DJ, Loe YC, McEvoy-Hein BK, Hellerstein MK (2007) Effects of modified alternate-day fasting regimens on adipocyte size, triglyceride metabolism, and plasma adiponectin levels in mice. J Lipids Res 48(10):2212-9
Calorie restriction (CR) affects adipocyte function and reduces body weight. However, the effects of alternate-day fasting (ADF) on adipose biology remain unclear. This study examined the effects of ADF and modified ADF regimens on adipocyte size, triglyceride (TG) metabolism, and adiponectin levels in relation to changes in body weight and adipose mass. Twenty-four male C57BL/6J mice were randomized for 4 weeks among 1) ADF-25% (25% CR on fast day, ad libitum on alternate day), 2) ADF-50% (50% CR on fast day), 3) ADF-100% (100% CR on fast day), and 4) control (ad libitum). The body weight of ADF-100% mice was lower than that of the other groups (P < 0.005) after treatment. Adipose tissue weights did not change. Inguinal and epididymal fat cells were 35-50% smaller (P < 0.01) than those of controls in ADF-50% and ADF-100% animals after treatment. Net lipolysis was augmented (P < 0.05) in ADF-100% mice, and the contribution from glyceroneogenesis to alpha-glycerol phosphate increased in ADF-50% and ADF-100% mice, whereas fractional and absolute de novo lipogenesis also increased in ADF-50% and ADF-100% animals, consistent with an alternating feast-fast milieu. Plasma adiponectin levels were not affected. In summary, modified ADF (ADF-50%) and complete ADF (ADF-100%) regimens modulate adipocyte function, despite there being no change in body weight or adipose tissue weight in the former group.
Showing posts with label 2007. Show all posts
Showing posts with label 2007. Show all posts
Wednesday, January 20, 2010
From the LATimes: Feast, fast and reduce risks
Originally published decemeber 10, 2007 in the LATimes.com
http://www.latimes.com/features/health/la-he-eat10dec10,1,883044.story
Feast, fast and reduce risks
An irregular eating cycle worked for ancient humans. Small studies show benefits in such calorie restriction.
By Susan Bowerman, Special to The Times
Our hunter-gatherer ancestors spent hours each day searching for food that was only intermittently available. They'd fast, and then they'd feast. These ancient humans developed a "thrifty" genotype that helped them adapt to these cycles of want and plenty.
Today, we carry this same genetic makeup with us, and several animal studies and few small human trials indicate that there may be, for us too, health benefits to alternate-day fasting -- a regimen that somewhat mimics the irregular and unpredictable food intake pattern on which our ancestors evolved.
Evidence has been accruing for some time that chronic calorie restriction, in which daily intake is reduced to between 60% and 85% of an individual's daily needs, appears to have significant health benefits. Such restriction has been shown to reduce risk factors for several chronic diseases in animals and humans and to increase life span in rats, mice, fish, flies, worms and yeast.
But the effects of alternate feast and fast days on body weight and health have only recently been explored.
In a study published in the American Journal of Clinical Nutrition in 2005, scientists at the Pennington Biomedical Research Center examined the effects of alternate-day fasting on heart disease risk in 16 subjects.
Subjects ate whatever they wanted on feast days but consumed only calorie-free beverages and sugarless gum on fast days. After three weeks, blood levels of triglycerides fell in men, but not in women. Women, but not men, experienced increases in "good," or HDL, cholesterol.
There was no clear explanation for the differing results between men and women, but the same group of scientists have observed other sex-specific effects. In a different report, they measured the rise in insulin and blood sugar levels in response to a meal before and after three weeks of alternate-day fasting.
Men -- but not women -- had increased insulin sensitivity so that they cleared sugar from the bloodstream more efficiently after three weeks on the regime, suggesting that alternate-day fasting may be more beneficial to men than women in reducing the risk of Type 2 diabetes.
Similar improvements in insulin sensitivity were observed after two weeks of alternate-day fasting in a small study of eight male subjects at the University of Copenhagen, published in the Journal of Applied Physiology in 2005.
The effects of alternate-day fasting on body weight differ according to the study (and none have been reported in overweight people). Men in the Copenhagen study maintained a stable body weight over the two week period -- but they were specifically instructed to attempt to do so.
In the Pennington study, subjects were informed that they would need to double their usual intake on non-fasting days in order to maintain their weight. But taking in enough food on the feasting days to avoid weight loss proved difficult. The participants lost about 2.5% of their initial weight and 4% of their initial fat mass.
All in all, the few human studies on alternate-day fasting have been small in size, short in duration and have lacked control groups so more studies are warranted. Still, the animal studies suggest that the effects of alternate-day fasting on chronic disease prevention are similar to those reported for chronic calorie restriction.
How such dietary calorie restriction may impart its benefits is not clear, but it may include increased resistance to stress, a reduction in free-radical production (which in turn reduces cellular damage) or the slowing of certain metabolic processes that might damage the body.
From a practical standpoint, it's unclear whether people could stick to an alternate-day fasting regimen for any length of time. Researchers have suggested that the regimen is easier than daily calorie restriction, but is it easy enough? Many subjects in the Pennington study reported feeling hungry and irritable on the days they fasted -- and that would probably limit the number of people who could sustain this pattern of eating for very long.
Anyone wishing to attempt either chronic or alternate-day calorie restriction needs to remember that consuming nutrient-dense foods is key. There are no extra calories to spare, so every bite of food needs to be packed with nutrition.
But a carefully planned diet based on vegetables and fruits, lean proteins, a few whole grains and small portions -- rather than a continuous and abundant food intake -- may be a better nutritional match for those "thrifty" genes.
Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.
http://www.latimes.com/features/health/la-he-eat10dec10,1,883044.story
Feast, fast and reduce risks
An irregular eating cycle worked for ancient humans. Small studies show benefits in such calorie restriction.
By Susan Bowerman, Special to The Times
Our hunter-gatherer ancestors spent hours each day searching for food that was only intermittently available. They'd fast, and then they'd feast. These ancient humans developed a "thrifty" genotype that helped them adapt to these cycles of want and plenty.
Today, we carry this same genetic makeup with us, and several animal studies and few small human trials indicate that there may be, for us too, health benefits to alternate-day fasting -- a regimen that somewhat mimics the irregular and unpredictable food intake pattern on which our ancestors evolved.
Evidence has been accruing for some time that chronic calorie restriction, in which daily intake is reduced to between 60% and 85% of an individual's daily needs, appears to have significant health benefits. Such restriction has been shown to reduce risk factors for several chronic diseases in animals and humans and to increase life span in rats, mice, fish, flies, worms and yeast.
But the effects of alternate feast and fast days on body weight and health have only recently been explored.
In a study published in the American Journal of Clinical Nutrition in 2005, scientists at the Pennington Biomedical Research Center examined the effects of alternate-day fasting on heart disease risk in 16 subjects.
Subjects ate whatever they wanted on feast days but consumed only calorie-free beverages and sugarless gum on fast days. After three weeks, blood levels of triglycerides fell in men, but not in women. Women, but not men, experienced increases in "good," or HDL, cholesterol.
There was no clear explanation for the differing results between men and women, but the same group of scientists have observed other sex-specific effects. In a different report, they measured the rise in insulin and blood sugar levels in response to a meal before and after three weeks of alternate-day fasting.
Men -- but not women -- had increased insulin sensitivity so that they cleared sugar from the bloodstream more efficiently after three weeks on the regime, suggesting that alternate-day fasting may be more beneficial to men than women in reducing the risk of Type 2 diabetes.
Similar improvements in insulin sensitivity were observed after two weeks of alternate-day fasting in a small study of eight male subjects at the University of Copenhagen, published in the Journal of Applied Physiology in 2005.
The effects of alternate-day fasting on body weight differ according to the study (and none have been reported in overweight people). Men in the Copenhagen study maintained a stable body weight over the two week period -- but they were specifically instructed to attempt to do so.
In the Pennington study, subjects were informed that they would need to double their usual intake on non-fasting days in order to maintain their weight. But taking in enough food on the feasting days to avoid weight loss proved difficult. The participants lost about 2.5% of their initial weight and 4% of their initial fat mass.
All in all, the few human studies on alternate-day fasting have been small in size, short in duration and have lacked control groups so more studies are warranted. Still, the animal studies suggest that the effects of alternate-day fasting on chronic disease prevention are similar to those reported for chronic calorie restriction.
How such dietary calorie restriction may impart its benefits is not clear, but it may include increased resistance to stress, a reduction in free-radical production (which in turn reduces cellular damage) or the slowing of certain metabolic processes that might damage the body.
From a practical standpoint, it's unclear whether people could stick to an alternate-day fasting regimen for any length of time. Researchers have suggested that the regimen is easier than daily calorie restriction, but is it easy enough? Many subjects in the Pennington study reported feeling hungry and irritable on the days they fasted -- and that would probably limit the number of people who could sustain this pattern of eating for very long.
Anyone wishing to attempt either chronic or alternate-day calorie restriction needs to remember that consuming nutrient-dense foods is key. There are no extra calories to spare, so every bite of food needs to be packed with nutrition.
But a carefully planned diet based on vegetables and fruits, lean proteins, a few whole grains and small portions -- rather than a continuous and abundant food intake -- may be a better nutritional match for those "thrifty" genes.
Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.
Alternate-day fasting and chronic disease prevention: a review of human and animal trials
Varady KA and Hellerstein MK (2007) Alternate-day fasting and chronic disease prevention: a review of human and animal trials. American Journal of Clinical Nutrition, Vol. 86, No. 1, 7-13, July 2007
http://www.ajcn.org/cgi/content/full/86/1/7
Abstract
Calorie restriction (CR) and alternate-day fasting (ADF) represent 2 different forms of dietary restriction. Although the effects of CR on chronic disease prevention were reviewed previously, the effects of ADF on chronic disease risk have yet to be summarized. Accordingly, we review here animal and human evidence concerning ADF and the risk of certain chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. We also compare the magnitude of risk reduction resulting from ADF with that resulting from CR. In terms of diabetes risk, animal studies of ADF find lower diabetes incidence and lower fasting glucose and insulin concentrations, effects that are comparable to those of CR. Human trials to date have reported greater insulin-mediated glucose uptake but no effect on fasting glucose or insulin concentrations. In terms of cardiovascular disease risk, animal ADF data show lower total cholesterol and triacylglycerol concentrations, a lower heart rate, improved cardiac response to myocardial infarction, and lower blood pressure. The limited human evidence suggests higher HDL-cholesterol concentrations and lower triacylglycerol concentrations but no effect on blood pressure. In terms of cancer risk, there is no human evidence to date, yet animal studies found decreases in lymphoma incidence, longer survival after tumor inoculation, and lower rates of proliferation of several cell types. The findings in animals suggest that ADF may effectively modulate several risk factors, thereby preventing chronic disease, and that ADF may modulate disease risk to an extent similar to that of CR. More research is required to establish definitively the consequences of ADF.
http://www.ajcn.org/cgi/content/full/86/1/7
Abstract
Calorie restriction (CR) and alternate-day fasting (ADF) represent 2 different forms of dietary restriction. Although the effects of CR on chronic disease prevention were reviewed previously, the effects of ADF on chronic disease risk have yet to be summarized. Accordingly, we review here animal and human evidence concerning ADF and the risk of certain chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. We also compare the magnitude of risk reduction resulting from ADF with that resulting from CR. In terms of diabetes risk, animal studies of ADF find lower diabetes incidence and lower fasting glucose and insulin concentrations, effects that are comparable to those of CR. Human trials to date have reported greater insulin-mediated glucose uptake but no effect on fasting glucose or insulin concentrations. In terms of cardiovascular disease risk, animal ADF data show lower total cholesterol and triacylglycerol concentrations, a lower heart rate, improved cardiac response to myocardial infarction, and lower blood pressure. The limited human evidence suggests higher HDL-cholesterol concentrations and lower triacylglycerol concentrations but no effect on blood pressure. In terms of cancer risk, there is no human evidence to date, yet animal studies found decreases in lymphoma incidence, longer survival after tumor inoculation, and lower rates of proliferation of several cell types. The findings in animals suggest that ADF may effectively modulate several risk factors, thereby preventing chronic disease, and that ADF may modulate disease risk to an extent similar to that of CR. More research is required to establish definitively the consequences of ADF.
Subscribe to:
Posts (Atom)
