Blood type, Pioppi, gluten-free and Mediterranean – which popular diets are fads?

People with type B blood can still eat chicken and corn. Credit: Shutterstock

Each year, new weight loss diets appear that promise to reveal the ultimate secret of success – if only you buy the book, pills or potions.
Fad diets might achieve short-term results but they are difficult to sustain in the long term.

23 oct 2018--They often eliminate entire food groups, which means they're unlikely to provide adequate amounts of key nutrients that are essential for our health and well-being.
Fad diets and rapid weight loss can also increase the risk of serious health problems such as gall bladder disease and gallstones.

When assessing whether a diet is a fad, ask yourself, does the diet:

1. contradict advice from qualified health professionals?
2. promote or ban specific foods or whole food groups?
3. promote a one-size-fits-all strategy?
4. promise quick, dramatic or miraculous results with minimal effort?
5. focus only on short-term results?
6. promote "miracle" pills, supplements or products touted to "burn fat"?
7. make claims based on personal testimonials or one random study?

If the answer to two or more of these questions is "yes," it's probably a fad.
So, how do today's popular diets measure up? Here we road-test the blood type, Pioppi, gluten-free, and Mediterranean diets.

Blood type diet

The blood type diet has been around for some time. It's based on the idea that your blood type is a key factor in predicting your body weight, nutritional requirements, risk of chronic disease, and overall well-being.
According to this diet, those with blood type A should follow what resembles a vegetarian diet. Type Os are supposed to limit carbohydrates and increase their protein intake. Type Bs should avoid chicken, corn, wheat, lentils, tomatoes, peanuts, and sesame seeds; while type ABs should avoid caffeine, alcohol, and cured meats.
But a comprehensive review of 16 studies found there is no scientific literature to back up this list of dos and don'ts.
Verdict: Fad diet. It's highly restrictive and may increase the risk of nutrient deficiencies.

Pioppi diet

The Pioppi diet is promoted as resembling the food patterns of people living in the small village of Pioppi, southern Italy, who live long, healthy lives.
The traditional eating habits of the people of Pioppi are in line with the Mediterranean diet, and include lots of vegetables, legumes, grains, fruit, fish, olive oil and nuts, as well as modest amounts of cheese, yoghurt, coffee and red wine, small amounts of meat, and very little sugar or highly processed foods.
But the 21-day Pioppi plan is very different to this. It forbids bread and other grains typically consumed in the Mediterranean. It promotes foods not usually consumed by the people of Pioppi, such as coconut fat.

There’s no need to forgo whole grains unless you have coeliac disease. Credit: Shutterstock/wideonet

People who follow the Pioppi diet might lose weight because they're consuming less energy, having eliminated entire food groups. But consuming saturated fats (polyunsaturated fat) and cutting out grains goes against the current evidence for good heart health.
Verdict: Fad diet.

Gluten-free diet

Gluten is a protein naturally found in wheat, rye and barley, plus some food additives.
People with diagnosed coeliac disease must eliminate gluten from their diet to avoid serious damage to their gut, but many people choose to avoid gluten as a weight-loss strategy.
Eliminating gluten does not automatically reduce your kilojoule intake or induce weight loss. But some gluten-containing foods such as pizza, bread, pasta and cakes are energy-dense, so removing them completely will reduce your total energy intake, which may lead to weight loss.
Gluten-free alternatives can be just as high in kilojoules as the gluten containing version, and sometimes can be higher in kilojoules.
Removing gluten-containing without considering what foods will replace them can also reduce your intake of important nutrients such as fibre, folic acid and other B vitamins.
Recent studies discourage unnecessary gluten-free diets due to the reduced intake of beneficial whole grains, which are key to a healthy diet and are associated with lower heart disease and cancer risk.
Verdict: Fad diet when used for weight loss in people who don't have coeliac disease.

Mediterranean diet

The Mediterranean diet has a strong focus on intake of core foods in addition to olive oil, coffee and wine, and low intake of meat, sugar and highly processed foods.
While the main focus of the Mediterranean diet is not weight loss, when combined with a kilojoule restriction, it can be effective for weight loss.
Among studies that did not prescribe an energy restriction, following the Mediterranean diet was not associated with gaining weight. The Mediterranean diet has also been shown to improve components of metabolic syndrome, even without weight loss.
Verdict: The Mediterranean diet isn't a fad but it doesn't guarantee weight loss unless you also restrict your total kilojoule intake.

The best approach to weight loss is to follow a healthy, balanced eating plan and to be physically active. Try to make small changes to your usual eating habits that you can live with.
If you need help or to check whether you are meeting your nutrient needs, consult your GP or a dietitian.
If you would like to learn more about weight loss, you can enrol in our free online course The Science of Weight Loss – Dispelling Diet Myths.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Crash diets are highly effective – new evidence

Credit: Voyagerix/Shutterstock.com

If you've ever tried to lose weight, you've probably heard that crash dieting isn't the best way to go about it. Although you may lose lots of weight initially, you won't be able to keep the weight off and may even end up being heavier than you were before. But our latest research suggests that this isn't always the case.

27 sept 2018--Most people are aware that being overweight is bad for their health, so it's not surprising that about half of the UK population is trying to lose weight at any given time. But many people struggle to stick to traditional diets long enough to achieve results.
Some people opt for a quicker, more drastic solution: crash dieting. These diets, otherwise known as total diet replacement (TDR) programmes, involve drastically reducing calorie intake to between 800-1,200 calories per day. (The usual calorie intake for a woman is 2,000 calories, and for a man it's 2,500 calories.) People on these diets consume nothing but specially formulated soups, shakes and bars for up to 12 weeks.
Although lots of retailers sell these TDR products, they are more effective when combined with support and encouragement from a dietitian or trained counsellor. This professional support helps dieters develop the skills to stick with the programme and keep the weight off once the programme is complete.
However, in the UK, GPs don't tend to refer people who are looking to lose weight to these programmes. This is because NICE, the agency that evaluates treatments for the NHS, doesn't recommend TDR programmes, perhaps because there wasn't enough evidence to support TDR when NICE published their guidance. But recent studies suggest that it may be time for NICE to reevaluate the evidence.

Time to reevaluate crash diets

For our study, which is published in the BMJ, we recruited 278 obese patients. Half were randomly assigned to a 12-week TDR programme, while the other half were assigned to see the practice nurse for advice on how to lose weight ("usual care").
After one year, those assigned to receive the TDR programme lost an average of 11kg, while those in the usual care group lost an average of 3kg. Using a tool that helps GPs estimate a patient's risk of having a heart attack or stroke in the next ten years, the people in the TDR group had significantly reduced their risk score.
The TDR group also had significantly greater improvements in blood glucose control than the usual care group. Perhaps most important of all, participants in the TDR group reported bigger increases in quality of life than people in the usual care group.
More people in the TDR group reported side effects, but the number of more serious side effects was similar across groups. Side effects that were more common in the TDR group than in the usual care group included constipation, headache, fatigue and dizziness.
This new evidence suggests that TDR is a safe and effective way to lose a large amount of weight. For now, though, TDR programmes are not available on the NHS. Those interested in losing weight using TDR have to pay for it themselves, which means that many people who could benefit from this treatment may be unable to access it.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Low carb, Paleo or fasting – which diet is best?

At this time of year, we are bombarded with books and TV shows telling us what we should be eating and how best to lose weight. Particularly in vogue are low-carb diets, Paleo diets and intermittent fasting diets. But which diet is the most effective for sustained weight loss – not to mention good health?

01 feb 2018--First, let's look at low-carb diets, which include Atkins, Dukan and, more recently, the Pioppi diet. The argument behind these diets is that carbohydrates are bad for us because they are broken down into glucose, which stimulates the release of insulin, and insulin helps the body store the energy from food as fat – especially around our middles.
What is missed in this argument is that it is not only carbohydrates that encourage us to make insulin. Foods high in protein and fat do this, too. Beef, for example, increases insulin to a similar level as breakfast cereals.
Related to low-carb diets are the evolutionary-type approaches, such as the caveman diet and the Paleo diet. These diets recommend shunning processed foods and following a diet similar to that of our ancestors in the Paleolithic period – a period that began about 2.6m years ago and ended about 12,000 years ago.
Definitions of this diet vary, but they tend to exclude grains, which often results in a low-carbohydrate diet. Dairy products are also avoided. Both low-carb and Paleo diets encourage eating plenty of fresh food, including vegetables, and little or no highly processed food.
Evidence suggests that low-carb diets can help you lose weight, reduce your risk of type 2 diabetes and, perhaps, your risk of heart disease. However, these three potential benefits are largely linked to the energy restriction they cause and are not directly related to avoiding carbohydrates.
The reason for the drop in energy (calorie) intake is that carbohydrates normally make up a large part of the Western diet. Banishing carbs makes it difficult to make up for the lost energy intake because the food industry is geared to providing plenty of carbohydrate-rich foods.
Other studies suggest that eating protein and fat keep you feeling full for longer, and may suppress appetite that way. However, more research is needed to prove this theory.
There is some evidence that a low-carb diet can help you lose weight, for up to six months. And a study of people with type 2 diabetes suggests that it can help reduce the need for diabetes medication, even after two years.
The news is not all positive, though. Paleo diets, in particular, can cause side effects, such a diarrhoea, headaches and weakness. And both Paleo and low-carb diets tend to be more expensivethan a regular healthy diet (as per government guidelines), and require careful planning to meet nutritional needs.

The Eatwell guide.

Fasting

Intermittent fasting diets, such as the 5:2 diet and the warrior diet, are another recent fad. They usually involve going for 14 to 36 hours with few or no calories.
The 5:2 diet involves eating a normal amount of calories for five days of the week and eating reduced calories (25% of normal calorie intake) on two non-consecutive days. The warrior diet involves eating just one large meal a day.
These types of diets have been shown to result in weight loss. In a study published in the International Journal of Obesity, the 5:2 diet not only resulted in a loss of over 6kg, on average, in overweight and obese women, over a six-month period, it also improved several important markers of health, including LDL cholesterol, triglycerides and blood pressure.
The important thing for people embarking on fasting diets to remember is: you need to meet all of your nutritional needs, as per the UK government's Eatwell guide.
The diets we've discussed almost all recommend eating more vegetables and less sugar, refined carbohydrates and highly processed foods. The advocates of these diets differ on the role of fats and carbohydrates, but they all encourage people to think more about food and take control of the food they eat.

Reclaiming the word 'diet'

The evidence seems clear, most diets are equally effective when it comes to weight loss. The important thing is to find a diet that works for you – one you can enjoy in the long term.
Perhaps we need to remember the origins of the word diet, coming from the Greek "diata", meaning way of life. This meaning has been adapted over time to mean a restriction. It's time we reclaim the word diet for its true meaning, and look to find ways of eating that are both enjoyable and improve health.
What we have learned from countries where people live long and healthy lives is that they tend not to focus on specific diets – counting calories, fussing about carbs – instead they eat local produce that is affordable and enjoyable.

This article was originally published on The Conversation. Read the original article.

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High-protein diets: Bad for the middle-aged, good for the elderly

Consuming high levels of protein - particularly animal protein - is a bad strategy if you're at midlife and aiming to live into old age, new research finds. But a study out Tuesday reveals that in older age, fortifying one's diet with more protein-rich foods appears to be a formula for extending life.

20 mar 2014--An article published in the journal Cell Metabolism says that, over an 18-year study period, middle-aged Americans who had the highest consumption of protein were more than four times as likely to die of cancer or diabetes, and twice as likely to die of any cause, than those whose diets were lowest in protein.

But a high-protein diet had the opposite effect on Americans 66 and older, a group of American and Italian researchers found. Those whose diets were highest in protein were 60 percent less likely to die of cancer and 28 percent less likely to die of any cause than were those whose protein intake was lowest.

"Your stage in life matters," said biogerontologist Valter Longo, director of the University of Southern California's Longevity Institute and lead author of the paper, which explores the role of dietary protein from the cellular level to the population level. "Some have said for years that proteins are bad. That's half right and half wrong."

Tapping a national database of 6,381 Americans' health and nutrition behaviors, Longo's team found that in people between the ages of 50 and 65, following a diet in which protein accounted for 20 percent or more of daily calories consumed increased the risk of death during the 18-year study period to levels comparable to the effect of smoking cigarettes.

Whether the remainder of those younger individuals' diet was dominated by fat or carbohydrates made no difference to the outcome. But the source of the protein mattered a great deal: for those whose sources of protein were heavily plant-based - nuts and legumes - the increased risk of dying of cancer declined and the increased risk of all-cause mortality disappeared altogether.

Among the study's older subjects, by contrast, the source of proteins was less important. What was important, said Longo, appeared to be that those entering a period of growing frailty reduced their loss of weight and muscle mass with a higher intake of a nutrient that helps sustain and build both.

The article by the U.S.-Italian team is the culmination of two decades of study that has coaxed the researchers to look for clues well outside the lab: Longo and his team have studied the dietary habits of a little town in Italy with a high concentration of centenarians, and have traveled to Ecuador to gather information on an exceptionally long-lived family congenitally deficient in a growth hormone linked to cancer.

The findings of Longo's team are in line with mounting research on the hazards of heavy consumption of red meats and the protective effects of plant-based nutrients. But unlike many large-population studies that have found links between poor health outcomes and animal protein consumption, the current study identified the potentially pivotal role that a hormone called insulin-like growth factor-1, or IGF-1, plays in driving age-related diseases such as cancer.

In a subset of the study's human subjects who submitted their blood for analysis, as well as in laboratory mice, Longo's team found that heavy protein consumption in middle age drove up levels of IGF-1. In the group's rodent experiments, higher IGF-1 levels - whether induced by high protein consumption or genetic engineering - promoted rapid cancerous growth when the researchers implanted 20,000 cancer cells under the animals' skin: 100 percent of these mice developed tumors.

Among mice that were fed a low-protein diet through middle age - and which therefore had lower IGF-1 levels - tumor formation was 10 percent to 30 percent lower.

At the same time, the researchers uncovered evidence that older mice were less able to absorb or process proteins. When they were fed high-protein diets, the older mice tended to maintain or increase their weight - a factor that appeared to keep them from becoming frail. By contrast, older mice fed a low-protein diet lost weight; that, says Longo, appeared to make them more vulnerable to diseases of aging.

IGF-1, produced largely in the liver, is essential to normal human growth and to the process of cell replacement after injury . But it is also implicated in a wide range of disorders associated with overgrowth and cell proliferation, including heart enlargement, the runaway cell growth common to all cancers, and obesity.

But while IGF-1's role in promoting tumor growth has long been recognized, its link to a high-protein diet appears to be a new.

"People will say, 'Here we go again: First you attack the fats, then you attack the carbohydrates, now it's the protein,' " Longo said. But over 20 years of research linking heavy protein consumption to diseases of aging, and eventually to higher IGF-1 levels, he said, "we never changed our mind": Americans' protein-packed diets "are hurting them in a major way."

Three Popular Diets Studied for Effects on Lipid Profile

South Beach and Ornish diets may reduce low-density lipoprotein cholesterol

04 april 2009-- The maintenance phases of the South Beach and Ornish diets reduce levels of low-density lipoprotein cholesterol, whereas levels are increased by the maintenance phase of the Atkins diet, according to research published in the April issue of the Journal of the American Dietetic Association.

Michael Miller, M.D., of the University of Maryland School of Medicine in Baltimore, and colleagues conducted a study of 18 adults who all completed a four-week maintenance phase of the three diets with a four-week washout period in-between, and who were assessed for the effects of the diets on lipids, endothelial function and C-reactive protein.

When the subjects were on the South Beach and Ornish diets, low-density lipoprotein cholesterol was reduced by 11.8 percent and 16.6 percent, respectively, versus an increase of 8.1 percent on the Atkins diet, the investigators found. When the researchers used brachial artery testing to measure flow-mediated vasodilatation, they found there was an inverse correlation with intake of saturated fat.

"These data suggest that during weight maintenance, less favorable biological effects are observed during a simulated, high-fat Atkins diet when compared to the South Beach and Ornish diet," the authors write. "The findings support additional study in subjects with visceral obesity and the metabolic syndrome, in whom an increased risk of coronary disease at baseline may be accentuated with chronic consumption of a diet that exhibits unfavorable effects on lipids and endothelial function."

Abstract
Full Text (subscription or payment may be required)

Four Different Diets — Four Similar Results

27 feb 2009--Diets emphasizing foods with varying proportions of fat, protein, or carbohydrate all confer the same degree and duration of weight loss, according to a New England Journal of Medicine study.

Some 800 adults with BMIs between 25 and 40 were randomized to one of four diet groups, with each participant having a caloric deficit of 750 kcal/day relative to baseline. There were diets with high- and low-fat components, high- and average-protein components, and varying degrees of carbohydrate content. (See hyperlinked table below.)

After 2 years, the amount of weight lost was similar among the four groups (most of the loss took place in the first 6 months). Those losing the most weight were those with the best attendance at group meetings.

In Journal Watch General Medicine, Abigail Zuger notes: "Perhaps the average dieter's enthusiasm for counting out 14 walnut halves for a high-fat dinner simply wanes, rendering the nutrient composition of all limited-calorie eating plans pretty much the same."

LINK(S):

NEJM article (Free)

NEJM editorial (Free)