evidence

Does fasting result in weight loss?

Posted on June 28, 2018June 30, 2018 by yvettemartyn

A study has found that people who restrict their eating to between 10 am and 6 pm and fast for the other 16 hours of the day lose 3% of their body weight.

The study which was published in the journal: Nutrition and Healthy Aging took 23 obese people who had to meet the following criteria:

BMI between 30-45 (this means obese)
Aged 25-65 years
Not going through the menopause
Sedentary to lightly active
Stable weight over the last 3 months
Non-diabetic
No history of heart disease or stroke
Non-smoker
Not a shift worker
Not taking medication for weight loss or to reduce lipid or glucose levels

The people in the study were instructed to only eat in the 8 hour window, but they could eat whatever they wanted and didn’t need to calorie count. Outside of these hours they were allowed to drink water, black tea, coffee and diet soda. The researchers took measurements at the beginning and end of the 12 week trial to assess their:

Body weight
Blood pressure
Heart rate
Total cholesterol, LDL (bad cholesterol), HDL (good cholesterol) and triglyceride levels
Fasting glucose
Fasting insulin

These results were compared to 23 individuals who has already taken part in a trial several years ago, between 2011-2015. They were the control group and had been asked to maintain their weight and not to change their levels of eating or physical activity.

The people in the 8 hour eating group noted down when they started and stopped eating each day. On average it was found that the participants had been adherent to the strict eating window on six out of seven days a week.

By the end of the trial six people in the fasting group had dropped out, leaving just 17 people who had completed the 12 week study. Although it should be noted that none of the dropouts said they left due to the diet.

So what happened to these 17 people compared to those in the control group?

They ate 300 less calories a day
They lost 3% of their body weight
Their BMI reduced
Their systolic blood pressure dropped by 7 mmHg

Sounds great did anything not improve?

Well some things stayed the same when compared to the control group, including:

Macronutrients, cholesterol and fibre intake
The amount of steps walked a day
Fat mass, lean mass and visceral mass
Diastolic blood pressure
Heart rate
Total cholesterol, LDL, HDL, triglycerides, glucose and insulin

But still weight loss right? Does this mean we should all start fasting… No, not so fast [pun intended]…

There are negatives in this study…

Only 17 people followed this eating regime for duration of the 12 week study.
The drop out rate was quite high with 1 in 4 who started the diet giving it up.
We only know that the participants were adhering to this eating window from their self-reported records, which is not an accurate assessment.
The study only looked at healthy obese individuals, therefore it doesn’t represent what would happen if non-obese people took on this eating regime or how it would impact on a obese person who for example had diabetes.
The best design for this type of experiment is a randomised control study, where people are randomly allocated to an eating regime. This was not one of those trials, instead it compared the people who were fasting to those who were in a different study several years beforehand. In this time the general population’s knowledge of weight control may have shifted and the availability of food and seasons may have been different.
The study was short as it only took place over 12 weeks, so we don’t know what would happen in the longer term.

What about those sugar free drinks could they have helped or hindered this weight loss?

People were allowed to drink caffeine in the form of black tea and coffee outside of the fasting hours which can affect the body clock. The principle of fasting is based on how the daily body clock regulates metabolism. So while the calories in these drinks are low, the impact on the body clock and therefore metabolism can be significant. I.e. another reason to cut down on your caffeine intake if you want to try this eating regime out.

Is the 10am- 6pm window the best time to eat if I want to fast for 16 hours a day?

This is a good window for fitting in three meals with a typical 9-5 job, as you can have a late breakfast, early lunch and early evening meal. However other studies have found that eating larger meals early in the day can produce better weight loss than eating your main meal in the evening. So more studies are needed to look at the effect of shifting this eating window to earlier in the day .

Vitamin D prevents colds and flus

Posted on February 17, 2017February 17, 2017 by yvettemartyn

A meta-analysis published in the British Medical Journal has found vitamin D supplementation cuts the rate of upper respiratory infections people experienced.

A meta-analysis looks at numerous studies which investigate the same topic and combines the data to look for trends. This one looked at 25 studies with 10933 participants. All the studies gave vitamin D to an intervention group and looked at the proportion who experienced one acute respiratory tract infection compared to those taking a placebo.

The studies took place in 14 countries over four continents and included both sexes and those aged from birth to 95 years of age.

The studies gave the dose of vitamin D in different ways

Bolus doses given at 1-3 months happened in 7 studies
Weekly doses were given in 3 studies
Daily doses were administered in 12 studies

The studies followed the participants from 7 weeks to 1.5 years. and all were randomised and double blinded. This meant the participants and the investigators didn’t know who were in each category.

19 of the 25 trials took blood from participants at the start to check their baseline vitamin D concentration, they ranged from 18.9 – 88.9 nmol/L.

The meta-analysis obtained the raw data from the studies and reassessed it.

Less people taking a vitamin D supplement had a respiratory tract infection

Overall the study found that significantly fewer participants experienced one acute respiratory tract infection if they were taking vitamin D supplementation compared to not taking it.

The authors found that the bolus doses (those given in bigger doses every 1 – 3 months) really weren’t that helpful and if the weekly and daily dosed individuals were assessed alone then it became even more significant.

If you take those who had low vitamin D levels to begin with <25 nmol/L you only need to give 4 people a vitamin D supplement to prevent one person from having a respiratory tract infection. If vitamin D level was above 25 nmol/L to begin with then this rises to 15 people needing to have the supplement to prevent an infection, but is still a significant result.

It found that side effects from vitamin D are rare.

So why is it that the bolus doses didn’t offer much protection, the study has suggested that if you give somebody a bolus of vitamin D then you are going to see a spike in the vitamin D blood concentration, which could have a knock on effect to the usual body processes that lead to activated vitamin D being made active or degraded.

What are the negatives of the meta-analysis?

The disadvantages of the study were that some data may be missing due to perhaps unpublished data, also some subgroups that were assessed had limited data.

Also, The studies didn’t tend to look at who adhered to taking the vitamin D, this could be a plus as the meta-analysis was an intention to treat study (this means it includes everybody, including those who were given the supplement and chose not to take it). This means that anybody who replicates this study by taking the vitamin D religiously should see at least the benefit that the study found.

The last issue was that very few of the studies actually confirmed an infection with laboratory confirmation. However, since these type of infections are normally diagnosed from history and examination, it is unlikely to be a big issue.

Low calorie sugar substitutes cause hunger later on

Posted on January 7, 2017February 16, 2017 by yvettemartyn

A study has compared the effect of drinking a beverage of sucrose against three low calorie sugar substitutes and found those eating the substitute versions ended up overcompensating their intake to eat more calories at their next meal.

The study took 30 men, of average BMI (21.7) and average body fat (17.6%). The day before the study they would undertake no vigorous exercise, eat a standard evening meal and fast for 10 hours. They would eat a standard breakfast and then have a drink mid morning which they had to consume within 15 minutes. The drink contained either:

0.44 g of artificial sugar aspartame
0.63 g of natural monk fruit, a plant native to china
0.33 g of stevia, a natural sweetener extracted from plant leaves
or 65 g of sucrose (the amount normally found in commercially available sweetened drinks)

The drinks were flavoured with strawberry and dyed with a pink food colouring so they looked and tasted similar.

The participants would then rate their appetite and mood every 15 minutes until the first hour. They would then receive lunch of fried rice and could eat as little or as much as they wanted. The amount they ate was monitored and participants were asked to keep a food diary to assess what they ate for the rest of the day. This was then added up to work out their daily intake of energy.

Blood was also taken to look at what happened to their blood glucose and insulin levels for 3 hours after the beverage intake.

It was a randomised crossover study, meaning all participants would come in for 4 separate days and try each of the sugar beverages over the study. There were at least 5 non test days in-between these test days. The participants were blinded so they didn’t know which drink they were having and so were researchers who assessed the outcomes and performed the analysis.

Overall the stevia and monk fruit were rated as slightly less sweet and more bitter than the sucrose and aspartame.

The low calorie sugars led to overcompensation of eating later on

Those eating the non-sucrose sugars (aspartame, monk fruit and stevia) had less calorie intake from the beverage but made up for it by eating more lunch. Over the entire day of food intake there was no difference between the amount of energy intake between the four drinks. So while the low calorie sugars saved energy intake from the beverage it led to an increased appetite and overcompensation of food intake later in the day.

The sucrose caused the blood glucose and insulin to spike soon after consumption, this was more stable in the other sugars initially but they caused a sharper rise in the glucose and insulin response following lunch. With no overall difference in glucose or insulin over the three hours between the four sugars.

The benefits of this research was that it was the first study to investigate the effect of monk fruit on energy intake, glycemic and insulin responses.

But it does have limitations, with only 30 participates, it wasn’t a large study and it was also a very short study looking at just one day per beverage, this doesn’t show you what would happen to energy intake and weight over weeks to months of intaking sugar substitutes.

While the study suggests that those who have a low calorie sugar substitute will eat more. If someone was to drink a low calorie beverage instead of a high calorie beverage and then ensured they stuck to a strict intake following this, it could promote weight loss.

The study also relied on participants recording what they ate and drank for the rest of their day in a food diary, this may not have been accurately recorded. To attempt to overcome this the researchers asked all participates to take photographs of what they consumed, it was reviewed by trained researchers and just one nutritionalist then entered the dietary data for consistency.

Fill up on beans

Posted on December 31, 2016June 28, 2018 by yvettemartyn

A study has looked into what makes you fuller, a meal of high protein meat vs high protein vegetables vs low protein vegetables and found the high protein vegetables led to the fullest stomachs.

The study took 48 healthy men, they ate a standardised meal prior to 8 pm the night before the test and the next morning they were fed one of 3 meals based on oven baked pastries with a filling of:

High protein meat which came with a side of potatoes
High protein beans which came with a side of split peas
or Low protein legumes with a side of potatoes and split peas.

The meals were matched for weight and came with equal quantities of water, with both the high protein meals being matched for energy, protein and fat content. The participants then evaluated how hungry they were for the next 3 hours and were then allowed to eat a meal of pasta bolognese and told to keep eating until they were comfortably full.

The study was organised so that participants came back to try all 3 different meals, 5 participants dropped out: 2 did so due to gastrointestinal upset and 3 because of a lack of time, leaving 43 people in the study.

High protein legume meal was less palatable but more filling

Interestingly the high protein legume meal was felt to be much less palatable than the low protein legume and high protein meat meals which were felt to be equally as satisfying.

Those who ate the high protein bean meal ended up having a lower appetite and ate less at the next meal compared with the meat (400 kJ less which was 12% less) and lower protein legume meal (440 kJ less which was 13% less). Despite the high protein meals having a similar energy and protein content the beans led to people feeling fuller.

The study authors question weather the fibre within the meals effected the results. The high protein legume meal had 25 grams of fibre per 100g, with the lower protein vegetable meal having 10g and the high protein meat meal having just 6 g, this could have led to participants feeling fuller due to the increased fibre content.

They do however highlight strengths of the study, such as having used real foods which can be easily replicated while other studies have compared meals made of unnatural products and supplements. The use of natural foods is the reason the study authors had issues matching the fibre content of the meals.

The study was part of a project called: ‘optimal well-being, development and health for Danish children through a healthy New Nordic Diet’ and was funded by the Nordea Foundation (which awards donations to those who promote good living in Denmark) and from The Danish Agriculture & Food Council. Furthermore one of the authors acts as a consultant for a number of companies including the Global Dairy Platform, McCain Food, McDonald’s and Weight Watchers.

Is a very high fat, low carbohydrate diet good for you?

Posted on December 12, 2016December 12, 2016 by yvettemartyn

As the American Journal of Clinical Nutrition publishes an article highlighting the beneficial aspects of a high fat diet, is such an indulgent diet really good for you?

The article in question is:

Visceral adiposity and metabolic syndrome after very high-fat and low fat isocaloric diets: a randomized controlled trial. It was performed by researchers at the University of Bergen in Norway.

So what did the study authors do? Well they recruited 46 men between the ages of 30-50, who responded to a advert in a local newspaper, they had to have a raised body mass index and waist circumference. They needed to have no food allergies or regular medications and no severe disease diagnosis.

They were assigned to eat a specific diet for 12 weeks, either a very high fat, low carbohydrate diet, where they would get 73 percent of their energy from fat. Or a low fat, high carbohydrate diet where 53 % of their energy would come from carbohydrates.

The participants were given a recipe book to help them with choosing meals that reflected their respective diet. All particpants took a vitamin tablet and companies supplied some additional ingredients such as butter, coconut oil, a sugar substitute and plant based carbohydrate alternative.

Avoid hydrogenated fats, specific plant oils, sugar and highly processed foods

It’s worth noting that both diets emphasised low processed and low glycaemic food. Both diets emphasised homemade meals. Both groups were told to avoid hydrogenated vegetable fat, specific plant oils, sugar and highly processed foods. They were also told to eat 500 grams of vegetables and fruits every day and to eat vegetables with every meal. The high carbohydrate diet were also told to try and incorporate fruit juice.

2 men withdrew before the experiment started and a further 4 dropped out early on and 2 men were excluded because they hadn’t complied with the diet, leaving 38 in the final numbers, 18 eating the high carbohydrate diet and 20 in the very high fat diet.

Overall both diets led to the participants having smaller waists, less fat on their abdomen and a reduction in weight and overall there were less fats circulating in their bodies. But we should take these results with a pinch of salt, firstly there really aren’t that many people in the trial, they’re also all men, all fairly young in age (30-50 years) and carrying no significant medical diagnoses.

The study is not really comparing like with like, to do that you would need a group of men eating their standard diet. What we have here is men who were told to eat one of two diets which both promoted whole foods and emphasised an intake of fruit and vegetables. Both diets used the same foods, but in varying quantities, so it can be argued that the benefits reflect eating whole foods over processed food.

The study ends with the following words, “Our study cautions against extrapolating short-term (1–2 mo) metabolic responses to longer-term effects of macronutrients on cardiometabolic risk.” i.e. just because we did this for 12 weeks, it doesn’t mean you will see benefits in the long term.