Wednesday, March 14, 2018

Which Diet Is Most Effective; Low Fat, Low Carb Or Mediterranean


The Study
In this well-designed trial, 322 overweight subjects were randomly assigned to either a low fat diet, a low carb diet or a Mediterranean diet for 2 years. By the end of follow-up, the low fat group had lost 6.4 lbs, the Mediterranean group had lost 9.7 lbs. and the low carb group lost 10.3 lbs. There were some other interesting results:

-The low carb diet was the toughest to adhere to and had the highest drop-out rate.

-The Mediterranean diet had a more beneficial impact on blood glucose and insulin levels in diabetics than the low fat or low carb groups.

-Several risk factors for heart disease improved more on the low carb and Mediterranean diets than on the low fat diet, including reductions in c-reactive protein, triglycerides and ratio of total to HDL cholesterol. The New England Journal of Medicine 2008; 359:229

Take Home Message
The research is really starting to show that a low fat diet is not the path to greater weight loss or improved health. This trial was extremely well designed and not only was the low fat diet less effective for weight loss, it did not improve risk factors for heart disease and diabetes as much as the other two approaches. 

It is important to note that the subjects on the low carb diet were instructed to eat vegetable sources of fat and protein. This was not your typical low carb diet where the subjects were eating bacon, steaks and full fat dairy all day. In fact, when you choose healthy sources of protein and fat, the low carb diet looks a lot like a Mediterranean diet.

For me, the take home messages of this study are:
#1) Healthy fat is a good thing and does not need to be tightly restricted whether your goal is improved health or weight loss.

#2) Too many rapidly absorbed carbohydrates in your diet can make it harder to lose weight and can have a negative impact on your health. 

Is Alternate Day Fasting The Best Way To Lose Weight?


The Study
The efficacy and safety of alternate day fasting as a method of weight loss has not been proven despite the popularity of this weight loss strategy. A study recently published in JAMA Internal Medicine attempts to answer this question. In this investigation, 100 subjects were randomly assigned to one of three groups:

Alternate day fasting: these subjects consumed 25% of their energy needs on “fast days” and then 125% of their energy needs on alternate “feast days”.

Calorie restriction: these subjects consumed 75% of their energy needs each day.

Control group: these subjects had no intervention.

The trial consisted of a 6-month weight loss phase and then a 6-month weight maintenance phase. Primary outcome measures were weight loss and risk factors for heart disease. The results were fascinating:

1) Drop out rates were higher in the fasting group when compared to the calorie restriction group (38% vs. 29%).

2) There were no significant differences in weight loss between the two groups by the end of follow-up.

3) Mean LDL cholesterol rose significantly in the alternative day fasting group.
JAMA Internal Medicine 2017; 177:930-38.

Take Home Message
The results of this well-designed trial are not encouraging for proponents of alternative day fasting. Compared to a more conventional approach, fasting did not improve weight loss, was more difficult to follow and even had a negative impact on health, as higher LDL cholesterol translates to an increased risk of cardiovascular disease. 

Other studies I’ve reported on in this blog have shown evidence of glucose dysregulation with fasting (see them here). While we will wait for more research to be conducted in this area, it appears that fasting is not the way to go if weight loss and improved health are your goals.

Late Night Eating And Weight Gain


The right diet, a good cardiovascular exercise program and a full body resistance training program form the foundation of any weight loss strategy. However, other lifestyle choices can have a big impact on weight loss success. An example of one such lifestyle choice is to limit eating after 8:00 PM. This has been recommended to dieters for generations, but is there any research to back this up? Do people who eat a lot of food after 8:00 PM really gain more weight? In this post, we’ll take a look at what the research tells us.

I find this topic interesting for a couple of reasons. First of all, when I was in high school and college, I could not gain weight for the life of me. I ate all the time, but I had a really high metabolism and was extremely physically active, so I burned off every calorie I put into my body. This probably sounds like heaven to people who were struggling with their weight, but it wasn’t so great. I was really, really skinny.

One of my fraternity brothers told me that to gain weight, I just had to eat 2 peanut butter and jelly sandwiches right before I went to bed. I told him that those few hundred calories wouldn’t make a difference because I was already eating a ton of calories all day. He said it wasn’t just the extra calories, it was when I was eating them that was so important. I gave it a shot. The summer between freshman and sophomore year in college, I ate 2 peanut butter and jelly sandwiches right before I went to bed. I was also working in construction and lifting weights. I put on 30 lbs. in 4 months!

When I became a licensed nutritionist and started working with weight loss clients, I found that a lot of people who were overweight ate a high percentage of their food at night. Having them stop this habit, in addition to changes in diet and exercise, helped them to lose weight. I also noticed that clients that made good progress with their diet and exercise but did not stop eating late at night did not lose much weight at all. I have been recommending to limit late night eating to my weight loss clients for over 15 years.  So what does the research have to say about this?

The Research
Surprisingly, I did not find much high quality research on the topic of late night eating and weight gain. However, I did find several investigations utilizing weaker study designs that hint at a potential association.

1) In a recent cross-sectional investigation published in the American Journal of Clinical Nutrition, 110 college-aged men and women recorded all of their food intake with a time stamp so that the hour of consumption could be accurately recorded. When compared to normal weight subjects, overweight subjects consumed significantly more of their calories 1 hour closer to melatonin onset, which was around 11 PM (Reference 1).

2) Another cross-sectional investigation published in the journal Appetite showed that protein, fat and carbohydrate consumed after 8:00 PM were associated with a higher BMI in a group of 52 volunteers that filled out 7 day food logs (Reference 2).

3) This investigation is a much older study that only had an abstract. I include it here because it is interesting and I have never seen results like this before. In this study, 9 young men were given the same meal at 9:00 AM, 5:00 PM and 1:00 AM (Reference 3). Energy expenditure was measured by indirect calorimetry for one hour before, and six hours after consumption. Dietary induced thermogenesis (DIT) of the meal was calculated as the 3 hours of energy expenditure above basal metabolic rate.

Morning DIT was significantly higher than afternoon DIT (P=.04) and night DIT (P=.0002). Afternoon DIT was higher than night DIT (P=.06). What this means is that these young men burned a higher percentage of their meal’s calories in the morning than they did in the afternoon or at night.

Conclusions And Recommendations
The research on late night eating and weight gain is largely unimpressive. To come to a firm conclusion, you’d really want to see a number of randomized trials and well-designed cohort studies showing an association with late night eating and weight gain. To my knowledge, these studies have yet to be conducted. 

What we are left with are cross-sectional studies that are a much weaker form of evidence. Having said that, several studies I did find suggest a cross-sectional association between eating late at night and gaining weight. One study was a trial that mentions a potential mechanism, but it is so old I could not find the full text to properly evaluate it.

I would say the evidence, while weak, is suggestive of a relationship between late night eating and weight gain. So what are some potential mechanisms at play here?

1) Eating food late at night simply adds extra calories that you would not consume otherwise. 

2) Food consumed late at night is of poor nutritional quality and more likely to cause weight gain. Most people snack on high glycemic carbs like chips, pretzels and dessert late at night. These calories spike the blood sugar and increase fat storage.

3) Another hypothesis is that our metabolism slows down quite a bit at night, so more of what we consume is stored as fat.

4) The thermic effect of food is lower at night, so more of what we eat is stored as fat.

Despite the weak forms of evidence and uncertain mechanisms, I still think it is a good idea to limit eating after 8:00 PM if weight loss is your goal. I have seen this be a very big part of the equation for many weight loss clients over the years.

References
1) McHill AW, et al. Later circadian timing of food intake is associated with increased body fat. American Journal of Clinical Nutrition 2017; 106:1213-19.

2) Baron KG, et al. Contribution of evening macronutrient intake to total caloric intake and body mass index. Appetite 2013; 60:246-51.

3) Romon M, et al. Circadian variation of dietary induced thermogenesis. American Journal of Clinical Nutrition 1993; 57:476-480.