Monthly Archives: October 2012

Hurricane Sandy Approaches; meet Gabor Maté

Posted by on October 28, 2012 15 comments

I have a large number of half-completed posts and some will go up soon, but I thought I’d put up a note about the storm just so you’ll know what happened in case we lose power and disappear for a few days.

Hurricane Sandy looks to be an unusual storm: not terribly severe winds, but tremendous risk from flooding.

NOAA is projecting the storm will drop 6 inches of rain per day in some locations:

Wave heights are reaching 30 feet on ocean buoys:

The storm will make landfill with a full moon when tides are at their most extreme, so the potential for flooding to storm surges is severe. Widespread flooding means widespread power outages.

In Boston, they’re predicting four days of rain starting in a few hours.

If the rain has you at home looking for entertainment, here’s a very interesting talk by Gabor Maté, the Hungarian-Canadian psychologist (thank you, Kris!):

Be safe everyone!

Look AHEAD Scientists: Trying to Move the Deer Crossing

Posted by on October 22, 2012 78 comments

The Look AHEAD: Action for Health in Diabetes trial has been halted two years early. Here’s Gina Kolata in The New York Times:

The study randomly assigned 5,145 overweight or obese people with Type 2 diabetes to either a rigorous diet and exercise regimen or to sessions in which they got general health information. The diet involved 1,200 to 1,500 calories a day for those weighing less than 250 pounds and 1,500 to 1,800 calories a day for those weighing more. The exercise program was at least 175 minutes a week of moderate exercise.

But 11 years after the study began, researchers concluded it was futile to continue — the two groups had nearly identical rates of heart attacks, strokes and cardiovascular deaths.

It’s clearly a negative result for “eat less, move more” as a health strategy for obese diabetics.

Was “Eat Less Move More” Harmful?

A few Paleo bloggers are not surprised; indeed, Peter Dobromylskyj speculates that all-cause mortality – which Ms. Kolata and the NIH press release do not report – may have been higher in the “eat less, move more” intervention group:

It seems very likely to me that more people died in the intervention group than in the usual care group, but p was > 0.05.

Call me a cynic, but I think they stopped the trial because they could see where that p number was heading.

Peter may be a cynic but cynics are sometimes right, and I will bet that he’s right about this. In general, calorie restriction and exercise are better attested against cardiovascular disease than against other health conditions, so if death rates from CVD were identical in the two arms after 11 years, it’s quite likely death rates from other causes were higher in the intervention arm.

Our Theory

We discuss in our new Scribner edition two reasons why “eat less, move more” can backfire:

  • On a malnourishing diet, “eat less” means even greater malnourishment. Less of a bad diet is a worse diet.
  • Excessive exercise may over-stress the body and harm health. In diseased people, the volume at which exercise becomes excessive may not be that high.

On the other hand, ultimately some form of “eat less, move more” is needed if optimal health is to be attained:

  • An energy deficit – eating less than the body expends – is necessary to lose fat mass, and obesity is probably incompatible with optimal health.
  • About 20 to 30 minutes of exercise per day at the intensity of running or jogging is needed for optimal health, probably due to the role of daytime activity in entraining circadian rhythms (see “Physical Activity: Whence Its Healthfulness?”, October 11, 2012). Most people would need to “move more” to achieve this.

So the challenge in weight loss is two-fold: It’s necessary to adopt a healthy diet in which malnourishment doesn’t occur despite calorie restriction, and to find a healthy level of exercise that improves health without overstressing the body.

Look AHEAD: Bad Dietary Advice

The Look AHEAD Study Protocol tells us what the intervention group was told to do.

From page 29, here is the diet advice:

The recommended diet is based on guidelines of the ADA and National Cholesterol Education program [96,97] and includes a maximum of 30% of total calories from total fat, a maximum of 10% of total calories from saturated fat, and a minimum of 15% of total calories from protein.

This gives 55% carbs and probably 10% omega-6 fat. The omega-6 intake is far too high – for weight loss and good health, omega-6 intake should be less than 4% – and so is the carb intake – for diabetics, reducing carbs to 30% or less is highly desirable.

From page 30, here is the exercise advice:

The physical activity program of Look AHEAD relies heavily on unsupervised exercise, with gradual progression toward a goal of 175 minutes of moderate intensity physical activity per week by the end of the first six months. Exercise bouts of ten minutes and longer are counted toward this goal. Exercise is recommended to occur five days per week.

Moderate-intensity walking is encouraged as the primary type of physical activity.

I think this is reasonable advice. It translates to 35 minutes per day for 5 days. The intensity is quite low. This level of exercise is hardly likely to be excessive; indeed, it’s probably grossly insufficient for optimal health. It represents about a mile and a half of walking per day, five days per week. This may have been a homeopathic level of activity.

There is another reason the exercise may have produced no observable benefit. Since I believe the health benefits of exercise occur primarily through circadian rhythm entrainment, it’s likely that daytime exercise is much more beneficial than night-time exercise. Night-time exercise might be ineffective or even harmful to health if it disrupts circadian rhythms.

Unfortunately many people find it difficult to find time during the day for exercise. If the walking was performed at night, even the modest benefits of the activity may have been lost.

Weight and Health: What’s the Direction of Causation?

The one “success” of Look AHEAD was that it brought about some weight loss: the intervention group lost 5% of their original weight.

We know that obesity is associated with poor health. Since causation implies correlation, the existence of this correlation suggests that either (1) obesity causes poor health, (2) poor health causes obesity, or (3) some third factors cause both obesity and poor health.

The Look AHEAD study presumed (1) – that obesity causes poor health. The “eat less, move more” intervention was wholly directed at weight loss. If obesity is the cause of poor health, Look AHEAD should have improved health. It didn’t. This tells us that the direction of causality is either (2) or (3). Obesity doesn’t impair health; other factors that impair health cause obesity.

It’s easy to make faulty inferences about the direction of causation. The Look AHEAD scientists made the same mistake this woman did:

Conclusion

The basic flaw in the Look AHEAD study was that it was designed to bring about weight loss, and hoped that weight loss would improve health.

A better intervention would seek to improve health through a more PHD-like diet and through circadian rhythm therapies. Successful health improvement would, more than likely, lead to weight loss.

For the overweight and for diabetics, the focus should not be on weight, but on health. Improve health, and weight loss will follow. Focus on weight with a simple-minded “eat less, move more” intervention without tending to the quality of your diet and lifestyle, and you might be doing yourself more harm than good.

Very Low-Carb Dieting: Are the Hormonal Changes Risk-free?

Posted by on October 19, 2012 60 comments

I was in Chicago earlier this week to record a video discussion with Dr Ron Rosedale hosted by Dr Mercola. Ron and I have taken opposite sides in several “safe starch debates” (First installment here; reply to Ron here; Ancestral Health Symposium panel discussed here.) This new discussion was intended to be more cordial and uncover common ground as well as differences.

I was intrigued to see that Ron’s lunch consisted mostly of plant foods which he ate avidly; he said he believes that most people on his diet eat a significant amount of plant foods. I came away with the impression that the Rosedale Diet resembles the ketogenic version of PHD, only with less starch and MCT oil.

One of my objections to Ron’s recommendations has been that very low carb and protein consumption can be stressful to the body. Scarcity of carbs and protein invokes certain starvation-associated pathways – for instance, lower T3 thyroid hormone. We discussed this in “Carbohydrates and the Thyroid,” August 24, 2011.

Ron believes that low T3 on low-carb diets is healthy, and other low-carb advocates, such as Sam Knox, have made similar arguments.

I believe that intermittent fasting, which invokes starvation-associated pathways transiently, is usually health-improving – but that you can overdo it. What happens if you invoke these pathways chronically and continuously?

Prof Dr Andro on the “Athlete Triad”

Some light was shed on this question recently by Adel Moussa, aka Prof Dr Andro, who discussed the “athlete triad” in three posts (Part I, Part II, Part III) at his blog Suppversity.

The athlete triad appears most commonly in athletes who undereat and overtrain. Symptoms include low energy, amenorrhea in women and low testosterone in men, osteoporosis, reduced cognitive ability, and impaired immune function. The syndrome is surprisingly common, especially in female athletes:

Although the exact prevalence of the female athlete triad is unknown, studies have reported disordered eating behavior in 15 to 62 percent of female college athletes. Amenorrhea occurs in 3.4 to 66 percent of female athletes, compared with only 2 to 5 percent of women in the general population. [1]

As Adel discusses in Part II, the athlete triad is characterized by the following hormonal pattern:

  • low estrogen and testosterone levels
  • low T4 and low T3 thyroid hormone levels, often with low TSH and high reverse T3
  • a disturbed circadian cortisol rhythm lacking an appropriate cortisol spike in the morning and a normal decline in cortisol levels in the course of the day
  • low leptin, low insulin, and low IGF-1

Precisely the same hormonal patterns, including lower thyroid hormone levels, higher cortisol, and a suppressed circadian cortisol rhythm, are observed in total fasting and starvation. [2] [3]

These hormonal changes conserve glucose and protein, an appropriate step during starvation. The energy-intensive tasks of immune function and reproduction are temporarily suppressed until energy is more readily available.

Similar patterns of reduced T3 and elevated cortisol excretion were recently seen in a clinical trial of a 10% carb weight maintainance diet. [4] This trial shows that even in the absence of calorie restriction, carb restriction is sufficient to reproduce much of the “athlete triad”/starvation hormonal pattern.

This pattern reaches its most extreme form in anorexia:

[H]ypocaloric diets causes changes in thyroid function that resemble sick euthyroid syndrome. Changes consist of a decrease in total T4 and total and free T3 with a corresponding increase in rT3….

States of chronic starvation such as seen in anorexia nervosa are also associated with changes in thyroid hormone, GH, and cortisol secretion. There is a decrease in total and free T4 and T3, and an increase in rT3 similar to findings in sick euthyroid syndrome…. [T]here is an increase in GH secretion with a decrease in IGF-1 levels…. The changes in cortisol secretion in patients with anorexia nervosa resemble depression. They present with increased urinary free cortisol and serum cortisol levels. [5]

In chronic starvation, hunger is replaced by anxiety and a desire to move. In evolutionary context this urge to be active may have stimulated food-seeking, but in modern life it can exacerbate conditions like the athlete’s triad.

In Part II of his series, Adel made an interesting observation. Chris Kresser often mentions a patient who cured his health problems with pizza and beer. Here’s Chris recounting the story to Kurt Harris:

Chris Kresser: Back around 2000, I was interning for a holistic doctor down in San Diego, and this was before I got into Paleo or anything, and I was, I think, a vegan macrobiotic, for crying out loud, at that point!  So, we had a patient who was just really, really sick, and he was just getting sicker and sicker.  He weighed about 90 pounds.  I think he was about 6 feet tall.  And the doctor had him on a restricted diet, you know, one of those food allergy type of diets where all you’re eating is, like, broccoli, venison, and quinoa.

Kurt Harris:  The Specific Carbohydrate Diet?

Chris Kresser:  No, no, just like a really, you know, they do the IgG food testing, which is kinda bunk anyways.

Kurt Harris:  Yeah, that’s pretty bunk.

Chris Kresser:  And then they find out you can only eat strawberries, broccoli, quinoa, and ostrich!  You know?  And so, he was doing that, and he kept removing foods until he was literally down to, like, broccoli and steamed whitefish or something.  That was all he was eating.  And he just kept getting sicker and sicker.  So, he disappears for about six months, comes back a completely different person.  He’s back up to 160 or 170, which was his normal weight, you know, completely normal complexion.  Literally, we didn’t even recognize him, and the doctor was saying:  What happened?  Was it diet?  And the guy was like:  Yep, it was diet.  And he said:  Was it the candida diet?  Was it the Specific Carbohydrate?  What was it?  And he said:  It was the beer and pizza diet!  [laughter]  And this guy literally, I mean, the guy got to this point where he was like:  OK, if this is my life, I’m fine with just flaring out.  You know, this isn’t worth it.  And if I’m gonna go out, I’m gonna have fun.  And so, he started going out.  You know, he wasn’t ever hanging out with his friends anymore because he was on such a restricted diet, he had no social life, so he just said: Forget it.  I’m gonna drink beer and eat pizza at least three times a week, and then the other times I’m gonna do whatever I want.  And that completely restored his health.

Adel speculates (very plausibly in light of the man’s weight of 90 pounds!) that the patient was suffering from the starvation pattern which is replicated in very low-carb “euthyroid sick syndrome” and the athlete triad. What he needed was more calories, especially carb and protein calories. Pizza and beer are great sources!

Conclusion

It was a pleasure to chat with Ron and Dr Mercola in Chicago. We recorded a four hour discussion, which is going to be edited down to an hour or hour and a half.

We found plenty of common ground. We agreed that there are very real health benefits to low-carbohydrate diets. Low-carb diets are helpful against diabetes and metabolic syndrome, and quickly improve cardiovascular risk markers such as blood pressure, triglycerides, and HDL.

But in biology, good things can always be taken too far. One can restrict carbohydrates (and protein) too much. Extremism in carb restriction may, indeed, be a vice.

References

[1] Hobart J, Smucker D. The female athlete triad. Am Fam Physician. 2000 Jun 1;61(11):3357-64, 3367. http://pmid.us/10865930.

[2] Shimizu H et al. Altered hormonal status in a female deprived of food for 18 days. J Med. 1991;22(3):201-10. http://pmid.us/1770328.

[3] Palmblad J et al. Effects of total energy withdrawal (fasting) on the levels of growth hormone, thyrotropin, cortisol, adrenaline, noradrenaline, T4, T3, and rT3 in healthy males. Acta Med Scand. 1977 Jan;201(1-2):15-22. http://pmid.us/835366.

[4] Ebbeling CB et al. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA. 2012 Jun 27;307(24):2627-34. http://pmid.us/22735432.

[5] Douyon L, Schteingart DE. Effect of obesity and starvation on thyroid hormone, growth hormone, and cortisol secretion. Endocrinol Metab Clin North Am. 2002 Mar;31(1):173-89. http://pmid.us/12055988.

Physical Activity: Whence Its Healthfulness?

Posted by on October 11, 2012 101 comments

In our last post, Exercise: Is Less Better Than More?, I quoted four studies showing that light aerobic exercise, of the intensity of jogging at 10 or 11 minutes per mile, improved health up to a volume of about 30 minutes per day, but then the health benefits plateau. Light aerobic exercise seems to become unhealthy as the volume exceeds 50 minutes per day.

Today I’ll continue looking at low-level activity to try to clarify where the health benefits come from, so that we can better design a health-maximizing exercise program.

Sitting versus Standing

There seem to be negative health effects from even short periods – a few hours – of inactivity: sitting or lying down.

A recent systematic review, first-authored by TJ Saunders of Obesity Panacea, found that a single day of bed rest is sufficient to raise triglycerides, and that 2 hours of sitting increases insulin resistance and impairs glucose tolerance – moving the body closer to a diabetic phenotype. [1]

Research by Marc Hamilton found that sitting shuts down expression of lipoprotein lipase (LPL) in skeletal muscle, preventing muscle cells from importing fat. [2] A Science Daily article shows an interesting video based on this research. Here are blood samples after consumption of an identical meal eaten the same person; the left sample was taken after a meal eaten sitting down, the right sample after a meal eaten standing:

When sitting, dietary fats are taken up only by adipose tissue. When standing, they are taken up by muscle and adipose tissue both.

Time spent standing did more to push fat into muscle cells than vigorous daily exercise. This is significant because pushing nutrients into muscle cells promotes muscle growth. If you have trouble gaining muscle, maybe the problem is too much sitting, and what you need is not more intense workouts, but more frequent standing!

Sleep Is Good

Not all inactivity is bad, however. Sleep is highly beneficial.

Consequences of poor quality or insufficient sleep include:

  • Higher rates of cancer. [3]
  • Impaired immunity and vulnerability to infection. [4]
  • Higher rates of heart disease. [5]
  • Higher all-cause mortality. [6]
  • Faster cognitive decline with age. [7]
  • Shortening of telomeres. [8]
  • Higher rates of diabetes. [9]

One way to interpret this: Inactivity during the day is unequivocally bad, but inactivity at night may be a good thing.

This may be an indication that the benefits of activity come not through fitness, but through entrainment of circadian rhythms. To enhance circadian rhythms, we want daytime activity but night-time rest.

Activity at Work

If activity and exercise at work are good, it might seem a good thing to have an active job. Why not get paid for getting your exercise?

However, the data is not so clear. In comparisons of sedentary work with active work, usually the sedentary workers come out pretty well. For example:

  • In women, no relationship was found between occupational physical activity and heart disease risk. [10]
  • In the HUNT 2 study, people with metabolic syndrome were more likely to die of cardiovascular disease if their work included physical activity than if it was sedentary. [11]
  • In the Copenhagen City Heart Study, high occupational physical activity was associated with higher all-cause mortality. [12]

It seems that when it comes to routine physical activity, more is not better. Exercise is a stressor, and it’s easy to get too much. Being active for eight hours a day is too much.

How Much Activity is Optimal?

If we can easily get too much low-level activity, then what is the optimal amount?

I suggested in my last post that we don’t have an innate “activity reward” system in the brain because our hunter-gatherer ancestors got more exercise than they needed. If that’s true, then we can look to hunter-gatherers to see what constitutes enough activity.

So how much activity did hunter-gatherers get?

It’s been estimated that hunter-gatherers typically walk 5 miles a day, run 1 mile a day, and do various resistance-style carrying and lifting activities. For instance, anthropologist Kim Hill states:

The Ache hunted every day of the year if it didn’t rain. Recent GPS data I collected with them suggests that about 10 km (kilometers) per day is probably closer to their average distance covered during search. They might cover another 1-2 km per day in very rapid pursuit. Sometimes pursuits can be extremely strenuous and last more than an hour. Ache hunters often take an easy day after any particularly difficult day, and rainfall forces them to take a day or two a week with only an hour or two of exercise. Basically they do moderate days most of the time, and sometimes really hard days usually followed by a very easy day. The difficulty of the terrain is really what killed me (ducking under low branches and vines about once every 20 seconds all day long, and climbing over fallen trees, moving through tangled thorns etc.)

The Hiwi on the other hand only hunted about 2-3 days a week and often told me they wouldn’t go out on a particular day because they were “tired”. They would stay home and work on tools etc. Their travel was not as strenuous as among the Ache (they often canoed to the hunt site), and their pursuits were usually shorter. When I hunted with Machiguenga, Yora, Yanomamo Indians in the 1980s, my days were much, much easier than with the Ache. And virtually all these groups take an easy day after a particularly difficult one. [13]

So the Ache walked about 6 miles per day, ran about 1 mile; other groups did less, but all of them traversed more difficult terrain than modern walkers and runners. So it seems that 5 miles of walking and 1 mile of running per day on easy terrain might be a reasonable estimate for the optimal daily activity level.

Five miles is about 10,000 steps. A review of the evidence suggested that 7,000 to 11,000 steps per day achieves all the health benefits of walking. [14]

In a comment, Jason gave us a link to a Runner’s World article that contained figures from a recent paper [15]. These illustrate the plateauing of health benefits at a relatively low level of activity:

Above about 30 MET-hours per week of activity, corresponding to 2 hours per week (20 minutes per day) of running at 7 minutes per mile or 4 hours per week (40 minutes per day) of jogging at 10 minutes per mile, there are no health benefits to additional activity.

In other words, the benefits of exercise run out after running 3 miles or jogging 4 miles per day – not far from the hunter-gatherer activity level.

The shape of this curve is supportive of the idea that circadian rhythm enhancement, not fitness, is the cause of the health benefits of exercise. Levels of activity beyond running 20 minutes per day do increase fitness – every cross country or track team in the country trains at a higher level than this – but do not improve health; so health does not depend on fitness. It looks like we need a certain amount of activity to properly entrain our circadian rhythms – to tell our bodies that it is daytime, the time of activity – but once we’ve achieved that, we don’t need to do more.

Centenarians Don’t Over-Exercise

Dan Buettner, author of The Blue Zones: Lessons for Living Longer From the People Who’ve Lived the Longest, has said, “None of the longest-lived societies we studied exercise as we think of it.”

And, based on my readings of centenarian obituaries, it seems true that the longest-lived often don’t do a lot of exercise. A reader who has commented as “B.C.” emailed me a link to a New York Times story on Julia Koo, a centenarian who recently celebrated her 107th birthday in good health. Her secret to a long life: “No exercise, eat as much butter as you like and never look backwards.” [16]

Conclusion

It looks like if we want optimal health, at least four factors should influence our daily activity:

–          When it comes to vigorous activites like running, jogging, or lifting, we should do neither too much nor too little. A half hour of such activity per day may be optimal for health, an hour or more may do us more harm than good. Thus, occupations that require physical activity throughout the day may be health impairing.

–          Several hours per day of walking is probably beneficial.

–          The rest of the day should be restful, but not completely inactive. We should not go more than 20 minutes without standing.

–          There are reasons to believe that the benefits of activity may derive more from circadian rhythm entrainment than from fitness. If this is true, then it may be important to develop a routine that includes some activity every day, than it is to optimize fitness by a well designed high-intensity interval training and on-day/off-day protocol.

It really didn’t occur to me until we worked on the new edition of the book that circadian rhythms might be the reason for the health benefits of exercise. (We have more evidence in the book for this idea, including the observations that exercise in the day improves sleep quality at night, and that circadian rhythm disruption has similar health effects to sedentary living.) Since working through this research, I’ve become much more committed to doing something every day – but much less concerned about whether that activity is well designed to make me fit.

References

[1] Saunders TJ et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab. 2012; 2012:712435. http://pmid.us/22754695.

[2] Hamilton MT et al. Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes. 2007 Nov;56(11):2655-67. http://pmid.us/17827399.

[3] Nieto FJ et al. Sleep-disordered breathing and cancer mortality: results from the Wisconsin Sleep Cohort Study. Am J Respir Crit Care Med. 2012 Jul 15;186(2):190-4. http://pmid.us/22610391.

[4] Bollinger T et al. Sleep, immunity, and circadian clocks: a mechanistic model. Gerontology. 2010;56(6):574-80. http://pmid.us/20130392.

[5] Hoevenaar-Blom MP et al. Sleep duration and sleep quality in relation to 12-year cardiovascular disease incidence: the MORGEN study. Sleep. 2011 Nov 1;34(11):1487-92. http://pmid.us/22043119.

[6] Cappuccio FP et al. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. 2010 May;33(5):585-92. http://pmid.us/20469800.

[7] Altena E et al. Do sleep complaints contribute to age-related cognitive decline? Prog Brain Res. 2010;185:181-205. http://pmid.us/2107524.

[8] Barceló A et al. Telomere shortening in sleep apnea syndrome. Respir Med. 2010 Aug;104(8):1225-9. http://pmid.us/20430605.

[9] Botros N et al. Obstructive sleep apnea as a risk factor for type 2 diabetes. Am J Med. 2009 Dec;122(12):1122-7. http://pmid.us/19958890.

[10] Mozumdar A et al. Occupational physical activity and risk of coronary heart disease among active and non-active working-women of North Dakota: a Go Red North Dakota Study. Anthropol Anz. 2012;69(2):201-19. http://pmid.us/22606914.

[11] Moe B et al. Occupational physical activity, metabolic syndrome and risk of death from all causes and cardiovascular disease in the HUNT 2 cohort study. Occup Environ Med. 2012 Sep 28. [Epub ahead of print] http://pmid.us/23022656.

[12] Holtermann A et al. Occupational and leisure time physical activity: risk of all-cause mortality and myocardial infarction in the Copenhagen City Heart Study. A prospective cohort study. BMJ Open. 2012 Feb 13;2(1):e000556. http://pmid.us/22331387.

[13] O’Keefe JH et al. Exercise like a hunter-gatherer: a prescription for organic physical fitness. Prog Cardiovasc Dis. 2011 May-Jun;53(6):471-9. http://pmid.us/21545934.

[14] Tudor-Locke C et al. How many steps/day are enough? For older adults and special populations. Int J Behav Nutr Phys Act. 2011 Jul 28;8:80. http://pmid.us/21798044.

[15] Chomistek AK et al. Vigorous-intensity leisure-time physical activity and risk of major chronic disease in men. Med Sci Sports Exerc. 2012 Oct;44(10):1898-905. http://pmid.us/22543741.

[16] James Barron, “Lessons of 107 Birthdays: Don’t Exercise, Avoid Medicine and Never Look Back,” The New York Times, September 24, 2012, http://cityroom.blogs.nytimes.com/2012/09/24/lessons-of-107-birthdays-dont-exercise-avoid-medicine-and-never-look-back/.