Do Low Fat Diets Prolong Life?

There is hot debate (and much buzz in the media) these days as to whether low fat diets are good or bad for us, and whether we have gone overboard in promoting low fat as the way to go in guidelines over the last several decades.

A recent study, published in the British Medical Journal, conducted a systematic review and meta analysis, with their goal actually being to determine whether dietary lifestyle interventions targeting weight loss reduces mortality, cardiovascular disease, and cancer in people with obesity.  They hadn't intended to study low fat diets in particular, but out of the 54 randomized clinical trials that they identified for analysis, all but one of these trials described a low fat diet being included as at least one of their interventions (and all but three trials included some form of exercise advice). The diets were also usually low in saturated fat.

In this analysis of over 30,000 clinical trial participants in studies of at least 1 year duration, they found that weight loss interventions decreased mortality by 18%, corresponding to 6 fewer deaths per 1000 participants in the studies.  Weight loss after 1 year was 3.4kg (7.5lb), and about 2.5kg (5.5lb) after 2-3 years.

That this study found that dietary interventions reduce mortality in people with obesity is noteworthy, as the amount of weight lost was fairly low, and also because singular diet studies have not shown a reduction in mortality.  In fact, the only obesity studies that have really shown a reduction in mortality are those of bariatric surgery.  It is encouraging that perhaps a mortality benefit from lifestyle intervention emerges when we look at enough people together (as in the current study).

But does this mean that low fat diets are the way to go?   Not necessarily.

It is true that we cannot know if the benefits seen in this study were because of the weight lost, because of the low fat nature of the diets, or a combination of both.

However, a problem with the low fat diet approach in real life (ie outside of a clinical trial) is that it most often results in overconsumption of carbohydrates, which has likely contributed to the increase in obesity that we have seen in the last several decades.  The Mediterranean diet, which is not a low fat diet (fat intake is 35-47% of total calories, with a focus on the healthier unsaturated fats), has been shown to be associated with a reduction in mortality (in systematic reviews and meta analyses of cohort and case control studies). 

We must also remember that all systematic reviews and meta analyses of studies are subject to limitations in interpretation as they are compiling data from a variety of different studies, so they must all be taken with a grain of salt.

BOTTOM LINE: This study suggests that weight reducing diets (which happened to be mostly low fat diets) may reduce mortality.  I would now like to see more studies of diets with moderate carbohydrate restriction and more generous unsaturated fat intake to understand if these diets may have the same benefit.

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www.drsue.ca © 2017

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Could Artificial Sweeteners Cause Weight GAIN?

While artificial sweeteners have previously been touted as an excellent way to replace sugar in your diet and help with weight loss, they have in recent years been found to impact our biology in ways that may have adverse effects on our metabolism.  Rather than helping in a quest for weight loss, is it possible that sweeteners could actually cause weight gain and metabolic disease?

A recent systematic review and meta-analysis was recently published in the Canadian Medical Association Journal, which collected the currently available evidence to try to answer this question and received worldwide attention in doing so.  They included 37 trials (including 7 randomized controlled trials and 30 cohort studies), looking at a total of over 400,000 individuals (about 1,000 of whom were in the randomized studies).

In their analysis of the randomized controlled trials, over a median follow up of 6 months, they found no significant effect on body mass index (BMI) or measures of body composition.  So, use of sweeteners did not result in weight loss, but there was no weight gain seen either.

In the cohort studies, over a median follow up of 10 years, they found an increase in weight, BMI, and waist circumference, and a higher incidence of obesity, metabolic syndrome, type 2 diabetes, high blood pressure, stroke, and cardiovascular events.

So overall, none of the evidence assessed showed a benefit to weight, and the observational data suggested adverse effects of sweeteners on weight and health - none of which is good news.  And why is there a difference in conclusions between the randomized trials versus the observational (cohort) data?

Well, it's possible that the randomized trials were not long enough or big enough to show a negative impact on health, and that if they had been longer trials, perhaps results would have been different.

On the other hand, observational (cohort) data does not give us as trustworthy of an answer to any research question, because the results can be muddied by other factors. One concern is that these data may be confounded by 'reverse causation' - meaning that people with obesity, or those more prone to develop obesity (eg family history of obesity) are more likely to use sweeteners to help manage their weight (rather than the sweeteners being the cause of weight gain).

Either way, there is research to suggest biological mechanisms by which sweeteners could have an adverse impact on our metabolic health, particularly in relation to changes they induce in our gut bacteria, as well as our neurobiological response to these chemicals.  Further research is clearly needed to better understand their effect on our health.

Remember also that there is no doubt that excess sugar consumption is associated with weight gain and all of the above metabolic complications - so swapping sugar back in is not the answer either.

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www.drsue.ca © 2017

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Testing Blood Sugar - Is There A Point?

In the management of people with diabetes, we routinely equip patients with glucose meters and ask them to check sugars at home.  While the importance and utility of checking sugars at home for people using insulin is clear, there is much debate about whether this is useful for people with type 2 diabetes who are not on insulin.  A recent study, which got a lot of media hype, tackled this question.

The study, published in JAMA Internal Medicine, randomized 450 people with type 2 diabetes and not using insulin, to either a) no home glucose montoring; b) checking sugars once daily; or c) checking sugars once daily plus automated educational/motivational messages delivered to the patient from the meter.

The researchers found that there was no difference in diabetes control (A1C) nor health related quality of life after 1 year, and concluded that glucose monitoring in people with non-insulin-treated type 2 diabetes should not be routine.

I have some major beefs with this conclusion:

1.   Testing once a day does not tell a person very much about their blood sugar.   In order for home testing to be useful, I advise 'paired meal testing': checking before a meal, and checking again 2 hours later.  This can be very helpful to see how certain types of food affect your blood sugar, and can be help to eat mindfully and manage portion control.  I don't necessarily advise doing this every day: checking each of breakfast, lunch, and dinner once per week can be enough.  However, depending on what kind of medication a person is taking, I may recommend more often.  Also, if diabetes control is not great, then checks (in my opinion) should be done more frequently so that we can figure out how to bring down the sugars effectively and safely.

2.  As the authors note, the study was not powered to determine if there are benefits to checking sugars around the time of medication or dose changes.  It is very difficult for a doctor to know what the next best medication may be without knowing the pattern of blood sugars through the day.  Knowing the pattern of blood sugars is extremely important when new medications are added onto sulfonylureas and insulin in particular, because these medications can cause low blood sugar.  For example, if sugars are highest in the morning and lower later in the day, there is a risk of causing low sugars if a treatment is added that brings down sugars in the morning (as sugars later in the day will go down too).

3.  Compliance with sugar checks in the study was poor by one year, declining gradually over the year, with only about 55% of people in the monitoring groups checking sugars each day by the 1 year mark.  Interestingly, the diabetes control (A1C) was better at 3, 6, and 9 months in the glucose monitoring groups, compared to those not monitoring - perhaps the lack of difference in A1C by 1 year was due to the poor compliance with glucose checks by that point in time.

4.  The study team did not engage with patients after their baseline visit - meaning patients were on their own to interpret their blood sugars without help from the study team.  Their family doctors received a copy of blood sugar results, but the study did not collect info on what was done with that data, and these clinicians had minimal interaction with the study team.  

Diabetes is a team sport - an important part of the benefit of checking blood sugars is to discuss these results with your health care team for help in optimizing control.  While the setup of this study was intended to be 'real world', I would submit that what patients perceived as their 'health care team' during the study (their usual doctors plus study investigators) were not working as a team and this may have limited the best possible use of home glucose monitoring.  And perhaps compliance with checking sugars in the study would have been better if that team was working together and more engaged with the patients, as is the ideal model of care.  We are blessed in Canada to be able to say that for most people in our country, the 'real world' does consist of free access to a team to help each individual with their diabetes care.

5.  For any patient on a sulfonylurea (and of course insulin), sugars must be checked before driving.   For a paper to conclude that glucose monitoring should not be routine (in a study where 36% of patients were on sulfonylurea!) is inappropriate.

Unfortunately, the media took hold of this study and has been shouting from the rooftops that people with non-insulin-requiring diabetes do not need to check their blood sugar.    I would be most saddened if patients get the message that they should stop testing their blood sugars, and would strongly advise people to continue to follow their doctor or diabetes educator's recommendations on how frequent of sugar checks is appropriate.

I hope this blog helps to provide some balance and perspective on what I feel is a study full of limitations.

Disclaimer: I have received speaking honoraria from makers of glucose meters.

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2017

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Diabetes Medication Canagliflozin Reduces Cardiovascular Events

The eagerly awaited results of the CANVAS trial were just released yesterday at the American Diabetes Association Meeting, and published simultaneously in the New England Journal of Medicine.

The CANVAS program was a cardiovascular outcome trial of the SGLT2 inhibitor, canagliflozin (Invokana).  This program enrolled 10,142 people with type 2 diabetes and high cardiovascular risk, and randomized them to receive either canagliflozin 100mg, canagliflozin 300mg, or placebo, in addition to their usual care.

After a mean of 3.6 years, they found that canagliflozin reduced the risk of a combination of cardiovascular death, non fatal heart attack and non fatal stroke by 14%, with the benefit being particular to those with established cardiovascular disease at baseline.  The individual outcomes above were not significantly reduced when considered separately, but were significant when considered together.   Canagliflozin also reduced the risk of hospitalization for congestive heart failure by 33%, reduced the risk of poor kidney outcomes by 40% (a composite of a sustained 40% reduction in GFR, need for renal replacement therapy, or death from renal causes), and reduced progression of albumin in the urine by 27%.

In terms of risks of canagliflozin, unexpectedly, there was an increase in the risk of amputation, with 3.3% of people on canagliflozin requiring an amputation (most commonly a toe or forefoot) during the course of the trial, vs 1.5% in the placebo group.    There was also an increase in the risk of fracture, with 15.4 fractures per 1000 patient years on canagliflozin, vs 11.9 per 1000 patient years in the placebo group.  There was an increased risk of genital yeast infection, as expected for this class of medications, but no increased risk of urinary tract infection.

The CANVAS program adds to our understanding of the SGLT2 class of medications.   As the EMPA REG trial showed us that the SGLT2 inhibitor empagliflozin (Jardiance) also reduces CV events in people with type 2 diabetes and cardiovascular disease, this is looking more likely to be a 'class effect' of the SGLT2 inhibitors (we still await the DECLARE study of the SGLT2 inhibitor dapagliflozin (Forxiga) to be completed).

In terms of the risks seen in the CANVAS trial, much discussion is underway in the medical and scientific community, and more studies will need to be done to better understand these findings.  As always, the benefit vs risk of any medication must be carefully considered in finding the best medications for each individual patient.

Disclaimer: I receive honoraria as as continuing medical education speaker and consultant from the makers of canagliflozin (Janssen), empagliflozin (Boehringer-Ingelheim and Lilly), and dapagliflozin (Astra Zeneca).  I am involved in research of SGLT2 inhibitors as a treatment of diabetes. 

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New Class of Cholesterol Medication Prevents Heart Attacks

Statin medications have long been the main class of medications that have been recommended to lower cholesterol, as they have been shown to be very powerful to reduce the risk of cardiovascular events.  Now, a new class of medications joins the ranks of statins: the PCSK9 inhibitor evolocumab (Repatha) has been shown to reduce cardiovascular events.

The top-line results of the study, called the FOURIER study, have now been released.  This was a study of 27,500 patients with cardiovascular disease who were already on optimized statin therapy, randomized to receive either evolocumab or placebo.  They found that evolocumab reduced the risk of their primary endpoint, which was the sum of cardiovascular death, non fatal heart attack, non fatal stroke, hospitalization for unstable angina, or coronary revascularization (angioplasty).

I am looking forward to learning more about the results of this trial and the amount by which risk was reduced - these data will be released in March at the American College of Cardiology meeting in Washington DC.  It will be interesting to compare these results to the results of the IMPROVE-IT trial, which showed that the combination of statin therapy with the cholesterol lowering medication ezetimibe lowered the risk of cardiovascular death, major coronary events, or non fatal stroke by 2.0 percentage points compared to statin therapy alone.

It is encouraging to see a new class of cholesterol medications being developed that reduce cardiovascular events.  There are many patients who do not tolerate statin therapy; perhaps the PCSK9 inhibitors may also reduce cardiovascular risk for them (studies on this are currently underway).  PCSK9 inhibitors are extremely expensive, which limits their use in clinical practice.  Perhaps with these data, guidelines will be revised and we may hopefully see more coverage options so that the benefits of PCSK9 inhibitors to reduce cardiovascular events can be more widely enjoyed.

Disclaimer: I have been involved in a clinical trial of PCSK9 inhibition. I have received honoraria as a medical education speaker and consultant from the makers of ezetimibe (Merck).

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2017

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