Meal Timing, Glycemic Index & Load: Human Study Probes Whether "Hitting Your Macros" Really is All That Counts

High or low GI, carbs in the morning or in the evning, cookies and dingdongs or all bran. So many questions and way too many answers from rodent studies or studies in obese diabetics... but what are Mr. and Mrs. Healthy Average Joe supposed to do?

In a recently published paper, Linda M. Morgan, JiangWen Shi, Shelagh M. Hampton and Gary Frost take yet another look on a concept that has lost much of the momentum it had only a decade ago: The GI and / or GL paradigm (GI: glycemic index (abstract unit); GL: glycemic load, i.e. GI / actual amount of food) and combines another paradigm, which is still gathering momentum within the medical science community - the issue of nutrient timing, in order to answer the following questions:

• Will a large evening energy and carbohydrate load cause an increase in postprandial glucose that is comparable to the same amount of energy and carbohydrates in the morning?
• Will a high glycaemic excursions in the evening be ameliorated by decreasing the glycaemic index (GI) of the meal?

Or put simply: Does carbohydrate and energy timing make a difference and can this difference be mitigated by chosing the "right", i.e. low glycemic carbs (e.g. sweet potato vs. white bread)?

White bread king or all-bran pauper - is that  the question?

To answer this world-shattering question and actually prove their hypothesis that both, i.e. having carbs in the evening and having those in the form of high glycemic index foods, will have negative consequences on postprandial glycemia, the scientists picked six healthy volunteers (four females, two males; mean age 30 +/- 4.3 years, BMI 21·6 +/- 1.3 kg/m²) and randomly assigned them to a follow one of the four following dietary protocols:

• Low GI (average GI = 34), with the majority of energy load consumed in the morning (LGI-am)
• Low GI, with the majority of energy load consumed in the evening (LGI-pm)
• High GI (average GI = 84), with the majority of energy load consumed in the morning (HGI-am)
• High GI, with the majority of energy load consumed in the evening (HGI-pm)

with identical energy content of approx. 8368 kJ (2000 kcal) for the whole day on four individual intervention days with a minimum of 7 days between each of the tests. Breakfast was given at 09.30 hours, lunch at 13.30 hours and the evening meal at 20.30 hours - subjects were at the laboratory for the whole day. Blood samples were taken 2h postprandial and blood glucose levels were monitored continuously via a "MiniMed continuous glucose monitoring system" that senses interstitial glucose by electrochemical detection in subcutaneous interstitial fluid in 5 min intervals.

Figure 1: Composition of the two test diets (low GI, blue; high GI read) and individual macronutrient breakdown of the test meals the subjects consumed on two seperate occasions (based on Morgan. 2012)

It does not take a nutrition expert to see that despite the obvious differences with respect to the glycemic index and load, even the allegedly healthy low GI diet with all-bran for dinner* and a macronutrient composition 72% carbohydrates 14% protein and 14% fat is not exactly what the latest research would suggest to be a healthy, let alone a "physique enhancing" diet.

*note: The scientists probably chose similar foods for breakfast and dinner, because the study design required those to be exchangeable.

Against that background it is still astonishing how much of a difference...

• 99% higher fiber content,
• -60% lower glycemic index (GI), and
• -63% lower glycemic load (GL)

... actually make when it comes to the effect of isocaloric meals with identical macronutrient compositions (see figure 1, right):

Figure 2: Total area under the curve for interstitial glucose (0–20 h), postprandial plasma insulin, TAG (**mind the text for info a potential typo, here) and NEFA (0–2 h after each meal) in six healthy volunteers following either a high-glycaemic index (HGI) or a low-glycaemic index (LGI) diet, with most of the energy consumed either early (LGI-am, HGI-am) or late (LGI-pm, HGI-pm); all values expressed relative to respective statistical mean (data calculated based on Morgan. 2012)

I guess I don't have to tell you that the image that emerges here stands in line with the as of late largely ignored glycemic index paradigm the underlying message of which is: It is not simply the amount of sugar you eat,  but rather how fast / hard it hits your blood stream that determines it's impact of on your glucose metabolism. And with respect to the latter, the researchers remark:

"Glucose and insulin responses showed broadly similar patterns. Both meal timing and quality of carbohydrate affected postprandial glucose and insulin responses (P < 0.01). The area under the glucose and insulin response curves was greatest for the HGI-pm meal regimen. The HGI-pm meal regimen produced a significantly greater postprandial area under the glucose curve than for any of the other three meal regimens (P < 0.05). The postprandial area under the insulin curve was significantly greater than both the LGI regimens (P < 0•05). Postprandial insulin resistance measured by homeostatic model assessment was also significantly greater for the HGI-pm meal than for the two LGI meals (P < 0•05)."

However, since Morgan, Shi, Hampton and Frost also state that "[p]ostprandial TAG and NEFA levels were not affected by meal timing or carbohydrate quality", I do suspect that there is a typo in table 3 of the original study, where it says that the TAG would be 5.04 mmol/l x h (probably is 6.04) and thus more than 15% lower than the average (TAG levels and insulin resistance usually go hand in hand, so it is really very unlikely that the 5.04 mmol/l x h is correct).

So what's the take home message here?

The only question that still has to be answered would be "King or pauper? At least with regard to the former, the best thing I can to is to suggest you read both the posts on "Breaking the Fast" and the "Carbs Past 6PM Posts"  (Part 1 & Part 2). When you have done that your perspective on the importance of breakfast and the purported fallacy of having a large dinner should already have changed. The things that are still left to do is not fool yourself into the false belief that you can pound whatever junk you want (as long as it fits your macros). As the glucose curve of the high GI arms (light color) in the figure above goes to show you, your body won't be happy when you get your "carb macros" from sugary junk.

Stick to starchy (or "save carbs", if you will) and fruit. Use veggies to fill you up. Use coconut & olive oil and the fats that are already in your meats, fish and dairy products to achieve baseline fat intake of at least 40-50g (all together). Aim for a 100-120g carbohydrate basis, diverge towards the lower side, when your body fat is high, you can't train or you're dieting and towards the higher side, when you are already very lean, have a high training volume, or are trying to build muscle. Complement that with min. 20g of quality protein with each meal. Don't deprive yourself on any nutrient completely and ramp up the total amount of food (at the given ratio) to fulfill your energy requirements.

In that, avoid processed food sand rely on whole foods, whenever possible (>90%),. Use food supplements* only where it makes sense, e.g. a protein shake post workout (*creatine for example would not be a "food supplement", since you can NEVER get the amounts that are necessary to supersaturate your stores from meat alone) and don't forget to live about all that "dieting" and thinking about the best ways to eat, please!

So if we assume that my assumption with respect to the triglyceride values in the originally published study are correct and we are simply dealing with a typo here, the next questions which arise here, are...

1. What is / are the reason/s that the lipid metabolism did not suffer?
2. How reliable is the HOMA-PP, i.e. the postprandial assessment of insulin sensitivity via the homeostasis model assessment? 
3. What does all this mean for you? Does meal timing not make a difference and are macros all that counts? 

As far as (1) goes, the answer is pretty simple: With a diet that was that low in fat and not overabundant in energy (2,000kcal for both diets) any potential the negative downsides on lipid metabolism will take their time to show. The acute ingestion of three high GI meals on a single day or modifications in their distribution across the day won't have much of an effect in healthy individuals, such as the four women and two men in the study at hand (in diabetics and especially patients with NAFLD things will probably look different, though).

The absence of changes in lipid metabolism after one day on high vs. low GI diets w/ different meal timing patterns yields answer #1 to question (3): If you are healthy the occasional day with junk food won't hurt you as long as you keep the total amount of energy at bay and jump back on the "healthy diet" wagon the very next day.

On the other hand, if only a single day of high GI food consumption can have such a pronounced impact on the postprandial HOMA levels, this raises the question how reliable this "long term measure" of glucose sensitivity actually is. Obviously, you should not go to the doctor's office and have your HOMA measured, at a morning after a day with three SuperSize Meals from McDonalds (even if you have been fasting after supper at night before, as the participants in the study at hand did) - unless you want a prescription for meformin, of course ;-)

It would however be likewise unwise to "do everything right" for three (maybe even just one day) before you head to the doctor to get blood drawn, just to be able to rejoice over a HOMA reading that does by no means represent your "normal" insulin sensitivity. This may make your doctor happy and spare you getting ticked off, but could have you run around pre-diabetic unnoticed for months if not years - maybe so long until the first irreversible damage has already been done.

The high susceptibility of HOMA measures to acute dietary modifications yields answer #2 to question (3): If you want know where you stand, don't make last minute changes to your diet before you get blood drawn. After all, the 90:10 rule (better 95:5 rule ;-) applies both ways - the 90/95 days of consistent eating patterns will decide whether you are lean, muscular and above all healthy or fat, undermuscled and sick.


References:

• Morgan LM, Shi JW, Hampton SM, Frost G. Effect of meal timing and glycaemic index on glucose control and insulin secretion in healthy volunteers. Br J Nutr. 2012 Oct;108(7):1286-91.

Damsels in Distress: A Review

{image via Hollywood Reporter}

Whit Stillman's Damsels in Distress was released on DVD yesterday (Sept. 25th), and as the film only showed in a number of cities, I thought it might be helpful to review it for those who were not able to see the movie in theatres. Damsels in Distress, the first Stillman film since The Last Days of Disco in 1998, appears to be a bit of a departure from his Doomed Bourgeois trilogy, which explored the death of the WASP hierarchy, anti-Americanism abroad, and Society's role in mainstream culture. In this film, Seven Oaks College transfer student Lily meets three girls--Violet, Rose, and Heather--who recruit her to join their self-appointed crusade of reform at the school. Their mission includes assisting the hordes of affable but stupid frat boys into becoming more polished human beings, as well as fighting the growing campus trend towards suicidal tendencies with good hygiene and tap dancing.

Barcelona or Metropolitan this isn't. The Stillman trilogy's heroes--highly literate, self-serious Ivy League-educated 20-something year olds--ponder deep societal concerns, and the characters who don't fit this mold generally tend to be morally suspect, like Disco's devious Charlotte Pingress and Metropolitan's loathsome cad Rick von Sloneker (who boasts that he doesn't take his inherited European aristocratic title seriously).

 In Damsels, however, Stillman turns all this on its head. It is now the serious ones who are the problem. For example, our heroines frequently clash with the school newspaper's head editor, whose primary editorial activity in the paper (The Daily Complainer) is to rail against the fraternities and demand their ejection from the campus. When the girls stick up for the frat guys (on the principle that they are all lunkheads and thus need special assistance, not condemnation), the editor aims his snark at them and condescendingly mocks their volunteer work. This is not to say that the girls are complete fools. On the contrary, they are fairly sensible, intelligent women who are selflessly devoted to their causes. The main thrust of the film, embodied in the girls' crusades and behavior, is that is necessary to restore some sort of social order, but it has to be done without the self-serious conceit that plagues a good portion of the girls' peers.

{image via Senses of Cinema}

I found the way Stillman played with the theme of whimsical, lighthearted social reform interesting. The girls, with the exception of slightly aloof, jaded Lily, distinguish themselves from their peers with their outfits and manners. While the rest of the campus dresses in the standard collegiate jeans and sweaters, they don neatly pressed pastel frocks and prim cardigans. When confronted by their peers who portray them as silly or stupid, their responses are polite yet amusing in their earnestness. One of the suicide prevention center's regulars complains that "you think I'm going to kill myself and make you look bad," Violet assures her with "I'm worried you'll kill yourself and make yourself look bad." Even the camera focuses on the main characters differently; as my friend Alison, who saw the movie with me, remarked, golden light glows behind them like halos in the outdoor scenes. Their foes (and some movie critics) point out that the girls' dance-based suicide prevention techniques cannot address clinical depression and bipolar disorder--which require licensed therapy and medicine--but the girls do more than their classmate-detractors. They provide a friendly, welcoming atmosphere for their troubled peers and earnestly listen to and comfort them. One classmate, Jimbo, first visits the center to get help for a girl on his hall; as the movie progresses, he too volunteers at the center, and he and some of the "patients" become part of the girls' posse.

Despite the film's silliness--it concludes with a musical dance number à la Old Hollywood--I think it shares more in common with the Bourgeois trilogy than it seems to at first glance. The trick is that Damsels makes the same points as the trilogy, but in a moderate and lighthearted fashion. The trilogy is very concerned with social order; it praises traditional bourgeois values and bemoans the modern hedonistic lack of manners that lead to confusion and discord. In Damsels, the girls seek to bring happiness to the campus with their emphasis on clean bodies and dwellings and teaching the frat boys how to court women. Also, Violet's personal life was less than satisfactory--she'd been unpopular and weird growing up and her parents died--but she made the best of it by changing her name to Violet and creating a new persona for herself. Additionally, dance is depicted in the trilogy as a metaphor for social relations. Metropolitan praises high-WASP debutante balls as a microcosm of well-mannered society, and as Disco's Charlotte famously remarks, "You know the Woodstock generation of the 1960s that were so full of themselves and conceited? None of those people could dance." Damsels is all about dance. In addition to providing tap dance lessons for the depressed, Violet has choreographed a piece she hopes to turn into an international dance craze--the Sambola. Just as Damsels is Trilogy-lite, the Sambola is dance-lite. As you can see in the video, its four steps are just signature moves from other dances, such as the tango promenade, a horizontal cha cha, and dance breaks from both the cha cha and the rhumba. And it is through dance that the center's visitors become friends and achieve happiness.

The Sambola 

(It's quite easy; if Thor can do it, so can you!)

On a side note, the movie also manages to get a few jabs in at higher education, namely the arrogance that seems to accompany it. For example, the newspaper editor and one of Lily's suitors, a grad student obsessed with Catharism, make derogatory comments about the frat guys' unadulterated stupidity. Such insults aren't without their merit; one of the frat boys cannot distinguish between colors. However, this shortcoming is the product of his parents' snobbery. They believed color recognition to be too simplistic to be important to focus on and tried to force him into weightier studies without covering preschool and kindergarten level curriculum. This character, Thor, does actually want to receive an education. The scene in which he finally learns the different colors of the rainbows is adorable. Moreover, it is reminiscent of I Am Charlotte Simmons, which articulated that the earnest pursuit of knowledge is true education.

{image via Whit Stillman}

In general, this is an adorable, feel good movie. While it doesn't have the same serious tone of previous Stillman films, it has the same charm and quirk. Metropolitan is hands down my favorite Stillman film, but I can't wait to get Damsels in Distress on DVD.

And in case you haven't seen the trailer...