VIENNA — Adopting a vegetarian or semi-vegetarian diet to lose weight and improve health may not be as onerous as is typically assumed, as people can experience health benefits even if they only partially switch to plant-based foods. In addition, the diets may cost less than other healthy diets, suggests new research presented here at the European Congress on Obesity (ECO) 2018.
In one study, Zhangling Chen, PhD, from Erasmus MC Rotterdam, the Netherlands, and colleagues showed in more than 9600 individuals that increasing the proportion of plant-based foods in the diet was associated with reductions in body mass index (BMI) and fat mass, even after taking into account potential confounders.
"Our study suggests that a more plant-based and less animal-based diet, beyond strict adherence to vegan or vegetarian diets, may be beneficial for preventing overweight/obesity in middle-aged or elderly populations," said Chen in an ECO press release.
Adding that such a shift "does not require a radical change in diet or a total elimination of meat or animal products," she noted, "it can be achieved in various ways, such as moderate reduction of red meat consumption or eating a few more vegetables."
In another study, Hilary Green, PhD, Institute of Nutritional Science, Nestlé Research Center, Lausanne, Switzerland, compared the cost of following three diets among people who buy their groceries online, a US healthy, Mediterranean, or vegetarian diet, and found that a vegetarian diet cost approximately $2 per week less than the other two diets.
A trend towards a semi-vegetarian diet, a so-called "flexitarian" way of eating, may seem beneficial, but could be difficult to introduce to patients already struggling with their weight, Jason Halford, PhD, chair in biological psychology and health behaviour, University of Liverpool, UK, who was not involved in either study, told Medscape Medical News.
"One of the issues I would have is how we normalize flexitarianism in groups more vulnerable to obesity, because many people may assume meat is a standard part of the meal."
He continued, "While the adoption of a flexitarian or vegetarian diet will produce benefits, they are [more] likely to be adopted and produce benefits in a population that is already health-minded to do so."
Rather than adopting a "nagging" educational approach, Halford believes the best way to encourage a more flexitarian diet is to "alter the social norms around what an ideal meal consists of" by, for example, offering more vegetarian or vegan options on menus.
Every Little Helps: Replacing Small Amounts of Meat With Veg Has Benefits
Although there is evidence to suggest that following a vegan or vegetarian diet reduces the risk of obesity, it has not been clear whether varying degrees of adherence to a plant- versus animal-based diet affects overweight or obesity.
Moreover, it is not known whether such eating patterns influence measures such as fat mass and fat-free mass index (FFMI) in middle-aged and elderly individuals, who undergo age-related changes in body composition, losing muscle mass.
For their work, Chen and colleagues studied three subcohorts from the ongoing prospective Rotterdam Study, gathering data on 9641 individuals with a mean age of 64.2 years. The participants completed a semi-quantitative food frequency questionnaire at baseline for each of the subcohorts (1989–1993, 2000–2001, and 2006–2009).
From this, the researchers calculated a plant-based diet index that assessed the degree to which an individual followed a plant- versus animal-based diet, with plant foods given positive scores and animal foods given negative scores.
They also collated longitudinal data on height, weight, and waist circumference from examinations conducted every 3 to 5 years from 1986 onwards, as well as on fat mass and FFMI, as measured using dual-energy X-ray absorptiometry at follow-up visits from 2002.
Multivariate-adjusted analysis revealed that a higher diet index was associated with a lower longitudinal BMI.
In individuals with a score of 10 points, this translated to a 0.70 kg/m2 lower BMI versus those with a score of zero. Researchers say that such a change in score could be achieved by, for example, replacing 50 g of red meat per day with 200 g of vegetables.
The observed reduction in BMI was primarily explained by a reduction in fat mass, at a beta value of –0.57, and a smaller reduction in FFMI (beta = –0.13).
A higher diet score was also associated with a smaller waist circumference, at an average reduction of 1.82 cm, and a lower body fat percentage, at –0.99%.
Chen told Medscape Medical News that their findings show that, in terms of dietary intake, reducing or preventing obesity need "not be a very difficult thing to do…and we do not have to eliminate all animal product intake or make large changes to our dietary intake."
This, she believes, will "increase the confidence" of the general public in their efforts to combat obesity.
Crucially, Chen also expects that the findings will translate into reduced risks of obesity-related cardiovascular diseases, such as coronary artery disease, type 2 diabetes, and stroke, adding that "we have observed that a plant-based diet may be beneficial for the prevention of insulin resistance, prediabetes, and type 2 diabetes."
She pointed out, however, that further studies in other populations are needed to confirm the findings, and that although "a modest reduction of animal-based foods may be beneficial, we also need to recognize the importance of overall diet quality."
Online Shopping Expensive, Out of Reach for Those on Low Incomes?
Green and colleagues observed that more and more US consumers buy their groceries online, with an estimated $7 billion in sales in 2017 forecast to grow to $29.7 billion in 2021. And by 2025, it is estimated that 20% of all food shopping will be done online.
To examine the cost of healthy eating for individuals who buy their groceries exclusively online, the team developed 2-week menu plans for the US healthy, Mediterranean, and vegetarian dietary patterns, all aligned with the 2015–2020 Dietary Guidelines for Americans, and including meals, snacks, and beverages.
The nutritional composition of all the food items was determined using the US Department of Agriculture (USDA) nutrient database. The overall nutritional quality of each menu plan, as if consumed by a sedentary woman aged 19–50 years, was then assessed using the Nutrient Balance Concept (PLoS One. 2015;10:e0130491).
The team mapped each food item or beverage to the cheapest retail price on the Amazon Grocery and Gourmet Food online platform to estimate costs for their official food plans.
Although the omission of meat and poultry appears to have driven down the cost of the vegetarian diet, there was no corresponding reduction in nutritional quality compared with the other plans, and all three showed high nutritional quality scores with no significant difference between them.
The vegetarian diet, at an average cost of $108 per week, was cheaper than the Mediterranean diet at $121 per week (P < .05), and the US healthy diet, at $119 per week.
But all three diets were still much more expensive than the estimated range for an official USDA food plan, however, which could cost as little as $45.60 per week but up to $90.80.
This meant the average cost of the vegetarian plan, at $15.40 per day, was considerably higher than the thriftiest USDA healthy menu, at $6.50 per day.
Speaking to Medscape Medical News, Green said that based on their findings online grocery shopping does not seem to be affordable for people with low disposable incomes — the very group who may benefit the most from a healthier diet.
She pointed out that there is "always a compromise between income and time," saying that being able to buy groceries at the lowest cost requires a large time investment.
"If you've got time to go shopping in the supermarkets and go to the local market...you might be able to achieve," a healthy diet at a low cost, she observed.
Best Advice Is Cut Down on Red and Processed Meat
Green also warned that, when building their menu plans, vegetarians need to ensure they have a balanced diet.
"The only watch-out is that you've got enough variety in the diet. The thing about meat and eggs in particular is that you get complete protein, so if you're getting protein from plants, you just need a variety."
Overall, Green agreed with Chen and Halford that following a flexitarian diet is "easier," adding that "cutting down on red and processed meat is for sure a good thing."
Hilary Green and Gary Sweeney were employees of Nestec, part of Nestlé, when this study was conducted.
European Congress on Obesity 2018. May 25, 2018; Vienna, Austria. Abstract O6.2, Poster T2P4.
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Cite this: Vegetarian or 'Flexitarian' Diet Benefits Waistline and Pocket - Medscape - May 28, 2018.