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Meat and Weight Contol

A new study published in The American Journal of Clinical Nutrition is reporting an association with eating meat and weight gain. This is a fairly robust epidemiological study, but at the same time is a good example of how such information is poorly reported in the media, leading to public confusion.

The data is taken from the European Prospective Investigation into Cancer and Nutrition–Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out of Home and Obesity (EPIC-PANACEA) project. This is a long term epidemiological study involving hundreds of thousands of individuals, and is therefore a great source of data. We are likely to see many publications from from it. This one looked at the association of meat eating – poultry, red meat, and processed meat – with total weight.  From the methods:

A total of 103,455 men and 270,348 women aged 25–70 y were recruited between 1992 and 2000 in 10 European countries. Diet was assessed at baseline with the use of country-specific validated questionnaires. A dietary calibration study was conducted in a representative subsample of the cohort. Weight and height were measured at baseline and self-reported at follow-up in most centers. Associations between energy from meat (kcal/d) and annual weight change (g/y) were assessed with the use of linear mixed models, controlled for age, sex, total energy intake, physical activity, dietary patterns, and other potential confounders.

They found that an increase in 240 grams per day of meat in the diet was associated with a 2kg increased weight after 5 years (that’s about 5 pounds, or 1 pound per year). The BBC reported this study as finding:

A European study of almost 400,000 adults found that eating meat was linked with weight gain, even in people taking in the same number of calories.

and

Although it is not clear why meat would lead to weight gain in people eating the same number of calories, one theory is that energy-dense foods like meat alter how the body regulates appetite control.

I find that conclusion problematic in several ways. Let’s look at the study design. One primary weakness is that weight (after the initial weighing) was self reported in most centers. This is a odd study design, and I can only assume this was a matter of practicality. Regardless of reason, self-reported weight is a major weakness. However it pales in comparison to the fact that total caloric intake was estimated, not rigorously controlled. To put this into perspective, 1 pound per year is 3500 Calories, or 67 Calories per week on average. There is no way someone can estimate their caloric intake within 67 Calories per week – that’s less than 10 calories per day.

The notion that appetite control was responsible for the findings also contradicts the assertion that total caloric intake was the same – appetite can only affect weight by increasing caloric intake. The correlation itself is in question because of the self-reported weight. But if we take the correlation as a given, the easiest explanation is that people who consume more meat also tend to consume slightly more calories, which add up over the years. Another possibility is that increased consumption of meat might also correlate with slightly less physical activity.

Assigning a cause and effect is difficult because slight changes that are difficult to measure accurately can result in modest weight differences over years.

Also, the authors concluded:

Our results suggest that a decrease in meat consumption may improve weight management.

“Suggest” and “may” are appropriate in that statement, but were largely lost in the secondary reporting. Again – even if we take the correlation as a given, this kind of data cannot be used to assign cause and effect. It cannot be concluded, in other words, that reducing meat will help reduce weight. Perhaps people who are more hungry for other reasons consume more meat, and if they cut down on their meat consumption they will just replace those calories with other sources. Other studies show that it is the consumption of calorie dense foods that correlate with weight gain, which can either be high fat and protein or high sugar. Calorie density seems to be the common element – which makes sense as increased calorie density can easily lead to overeating total calories, and it only takes a small amount to result in the kind of weight differences typically reported by these studies.

What we don’t have is evidence that decreasing meat intake as an intervention aids in weight control.

Conclusion

This study is interesting, but ultimately does not add much to our knowledge of diet and weight. It is not evidence that diets with the same calories but of different types lead to different weight outcomes, as has been reported. It does add to the literature that suggests that calorie dense foods correlate with weight gain, and this is likely due to increased overall caloric intake. There may be other factors as well, such as total activity, effects on hunger, and even calorie efficiency – how efficiently our bodies extract calories from certain foods.

But I am also struck in such studies, even intervention studies, by how small the difference are among the various diet types. This leads me to the conclusion that varying the ratios of macronutients (protein, carbohydrates, and fats) is of little ultimate utility in weight control. These studies get much attention in the media, but it is often much ado about nothing.

Meanwhile, the more significant factors are basic things like portion control and regular exercise. For health reasons other than weight control eating more vegetables is also a good idea, and this is also a good way to reduce total caloric intake.

Posted in: Nutrition

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32 thoughts on “Meat and Weight Contol

  1. Hey Thanks, it’s nice to read the research critique before reading all the media hype, for once.

  2. landanimal says:

    I do agree that they are unjustified in concluding that meat is the culprit. But if we back away from reductionism for a minute, it is possible that we see a general trend related to a diet that is high in meat consumption vs one that is more plant-based. The fact that those who ate more meat could be indicative of something about the typical meat-eaters diet. I think this study does not support the idea of giving up meat entirely, but perhaps shifting to a more plant-based diet instead in order to gain the benefit of whatever factors associated with it promote weight control.

  3. xwolp says:

    I find many of these large studies are curiously flawed in so many ways… I can only suspect that some people think sample size makes up for everything.

    Both caloric intake and weight was self reported.. at least for the latter one your could do better by having a proper physical examination which also would clear up another thing: weight gain is not the same as fat gain. If you do not take bodyfat vs muscle mass into account I am no quite sure how you can interpret the effects of a high protein diet.

  4. xwolp – you are correct, and that is a factor I did not discuss. Weight gain could be muscle gain for all we know, and the protein was contributing to weight gain.

    Also – the weight gain may have been in people who were underweight. Perhaps protein is a good way to put on healthy weight.

    Just looking at weight change leaves too many variables unaddressed.

  5. Robin says:

    xwolp – how would you do a large diet study that isn’t self-reported? Like you suggest, the weigh in/body mass part of the study could be objectively measured, but the problem with all diet studies is that unless they’re conducted in controlled settings (prisons? hospitals?) there’s no way to really know what and how much people are eating.

  6. WilliamLawrenceUtridge says:

    One thing that always interests me – do the calories include fiber? If you test calories using the awesomely-named bomb calorimeter, you essentially burn the food and measure the heat. Fiber, though, will generate heat but will not turn into calories. Surely that is accounted for in the food calorie counts?

    Plus, to turn any dietary macronutrient into fat takes energy. For fat I think it’s around 3% (100 calories of fat turns into 97 calories of body fat). For carbs, I think it’s around 90%, while for protein it’s less – 80%? 67%? It’s the least efficient any way.

    Not to mention, an athlete (or at least someone who exercises) stores more energy (in terms of glycogen and fat droplets) inside the muscles, where it does less harm compared to intravascular or even subcutaneous. You render an athlete and a couch potato (that’s how they determined the algorithms for skinfold testing and under water weighing to determine body fat percentage – cooked corpses until they were easily-measured goo), even with the exact same percentages of body fat, I’m guessing they come out looking pretty much the same in jars but their life expectancies are different. Proxy measures aren’t the same thing as outcome measures.

    Ah well, science is tough and I’m sure the headlines will screw it up. But it’s quite possible they’re even right and eating meat does preferrentially lead to greater weight gain.

  7. “Conclusion: Our results suggest that a decrease in meat consumption may improve weight management.”

    No, that is an unsupported speculation, regardless of how reasonable that speculation may be. What can be concluded from the study (regardless of how good the data and resulting conclusion are due to study design) is that eating meat is associated with weight gain. The data support no other conclusions.

    At best, the results suggest it may be worthwhile to conduct a study designed to see if a decrease in meat consumption may improve weight management

    I don’t like it when a study includes speculation in the conclusion. Put what can be supported by the data in the conclusion and add an extra section for speculation or hypothesis for further research.

  8. Scott says:

    What can be concluded from the study (regardless of how good the data and resulting conclusion are due to study design) is that eating meat is associated with weight gain. The data support no other conclusions.

    I’d go beyond this to argue that there are sufficient potential concerns with the data and design that even that association should be considered very tentative. It’s the same old story – no one study is perfect, so no one study gives you a solid conclusion even on the existence of an association.

  9. LovleAnjel says:

    Even if this was a good study with usable results, all they can show is that people that eat a bit more meat weigh a bit more. Nothing about their actual state of health, morbidity or mortality, which renders the results useless for all except those really concerned about those last five pounds.

  10. Josie says:

    @Robin –you are totally correct. The self reported food intake is a major obstacle to overcome in diet studies.

    The uncertainty can be mitigated through participants keeping a food journal –they are requested to note down everything they eat and measure the portions. Some studies will even include prepackaged meals.

    This is still not ideal of course but the data instill more confidence in their …truthiness :)

  11. Shelley says:

    It seems to me that in the years studied, there was a substantial and widespread increase in the number of people who followed Atikins-style (low carb-higher protein) diets.

    Consequently, it would not be surprising to find that those who consume more meats are also those more likely to have ongoing weight problems (and subsequent weight gain).

  12. Werdna says:

    landanima:But if we back away from reductionism for a minute, it is possible that we see a general trend related to a diet that is high in meat consumption vs one that is more plant-based.

    What does that mean? How do you see a general trend without data that is controlled with respect to other confounding factors?

    WilliamLawrenceUtridge:Fiber, though, will generate heat but will not turn into calories.

    Insoluble fiber sure but not all fiber. Regular fiber is estimated by some sources as being between 1.5 – 2.5 Kcals/g. From my understanding insoluble fiber – depending on your locale – can be reported on a label as zero calories. IMHO these differences are negligible often offset by other sources of error.

    For example I was able to track my weight-loss over five months within 99% of my expected weight (this was through some heroic measures) without taking into account things like the TEF or fiber digestibility.

    With regard to this study in particular I’d expect that any extra loss (or gain) are outweighed (no pun intended) by simple measurement error.

  13. superdave says:

    I wonder if it is possible that eating meat has a correlation with under reporting caloric intake.

  14. @Karl, re: “I don’t like it when a study includes speculation in the conclusion.”

    Amen! Is it really too much to ask scientists to leave speculation out of the conclusion? Apparently. Speculation about causation (or implied causation) in particular seems to be almost routine, even in a perfect absence of relevant data.

  15. tmac57 says:

    Werdna- Interesting comment. Did you estimate your weight loss based on the direct correlation of calories in,regardless of the type of food?

  16. khan says:

    After I retired, I lost 80#; didn’t ‘eat healthy’ just got away from work.

  17. Stuartg says:

    “Conclusion: Our results suggest that a decrease in meat consumption may improve weight management.”

    Replace the word “may” by the semantically equivalent “may not” and an equally valid conclusion is reached.

    It may be idiosyncratic of me, but I tend to dismiss papers that use the term “may” in their conclusions.

  18. DLC says:

    Most people don’t have a good sense of the caloric content or portion size of the food they eat, often confusing amounts.
    this would tend to compromise self-reporting.

  19. Mark P says:

    They found that an increase in 240 grams per day of meat in the diet

    How can anyone eat this much “more” meat? I love meat, and regard vegetarians with intense suspicion but that’s three times what I aim for as a daily intake.

    Seriously, if you eat 240 grams of meat a day, I wouldn’t trust you to know the first thing about a decent diet.

    It would seem to me that that amount of meat is merely a proxy for other behaviours. Not very clever ones. I hope the “other confounding factors” include alcohol and drug use, at the very least.

  20. BillyJoe says:

    I don’t worry much about what I eat. If I feel like it, I eat it. But I run for an hour or so every weekday and run/walk/climb 25km over the hills every Sunday, so I figure I can afford the luxury of not having to worry about diet.

    I just need a study now to confirm my prejudices. :)

  21. Mark P, 240 g is just over half a pound… that is, two quarter-pound hamburgers. One for lunch, one for dinner. For meat-eaters, that doesn’t sound extreme to me.

  22. Alison “Mark P, 240 g is just over half a pound… that is, two quarter-pound hamburgers. One for lunch, one for dinner. For meat-eaters, that doesn’t sound extreme to me.”

    As an average height female meat-eater, I know I would gain weight if I ate a quarter-pound hamburger for lunch and dinner, even if it were a lower calorie alternative such as chicken. Also note, that’s “an increase in 240 grams per day of meat” I’m not sure of the baseline.

    An unrelated note:
    Maybe it’s how my brain works, but I’m not wild about plans that seem to impart almost mystical abilities for good or evil to particular foods or food groups (fats, sugars, carbs* are bads, etc). They are just too complicated for me. When I want to lose weight (and I feel up to it) I find that targeting the appropriate calorie intake, then tracking calories in each meal to hit that target works fine. Only cutting back on particular foods has never worked for me, it’s all in the calorie count.

    One thing I would be interested in is appetite/satiety response. If I’m on a losing weight calorie count, I’m general quite hungry, except immediately after a meal. If I’m on a healthy weight maintenance calorie count, I’m generally a little hungry most of the time. Tried the snacking on vegetables, doesn’t matter. Tried adding jogging, which just made me famished (instead of a little hungry). Not sure if this is just cognitive, age or if it’s just that evolutionary drive to store-up for famine, but it’d be nice to find a way to override that.

    *Although, I know that some people do need to control cholesterol, sugars, etc due to specific health concerns.

  23. BillyJoe “I don’t worry much about what I eat. If I feel like it, I eat it. But I run for an hour or so every weekday and run/walk/climb 25km over the hills every Sunday, so I figure I can afford the luxury of not having to worry about diet.”

    Oh, that’s going to play hell on your knees, better start taking those Glucosomine supplements. :)

  24. Werdna says:

    @Tmac57:Did you estimate your weight loss based on the direct correlation of calories in,regardless of the type of food?

    I’m not exactly sure what you mean by “regardless of the type of food” since I used websites and product labels to estimate my calories in.

    What I did was this:

    i) Went a few weeks attempting to change very little of my diet while tracking calories. I eat a lot of packaged foods so this wasn’t hard (however as I mention below I did weigh everything and found some surprises). This gave me a baseline to figure out the coefficient to multiply my BMR by to estimate my caloric spend. During the course of the week I went out of my way not to increase any exercise since this can be difficult to calculate correctly.

    ii) Reduced my intake to about 1500Kc/day and was ridiculously strict in calorie measurement. I weighed everything – even packaged foods. If I thought a food could not be estimated accurately – I’d eat something else. Sometimes giving up healthier foods in favor of unhealthier but more homogeneous foods.

    iii) Weighed in every day, same time.

    One thing I found interesting is that it’s dead easy to mis-measure something. Packaged foods can by my measurements differ by weight up to 20%. Many lower calorie options at fast food restaurants are useless since they are difficult to quantify simply because a significant portion of their calories comes from things like sauces that can’t be relied on to be portioned out in a uniform manner. Considering that many people start dieting by cutting back 20-30% from their estimated caloric spend. It seems reasonable that this could account for some or all of the cases of cases of the “I diet but don’t lose weight” crowd.

  25. rmgw says:

    What really gets lighter when one does not eat animal products is one’s conscience – it is purely an ethical isssue.

    “After I retired, I lost 80#; didn’t ‘eat healthy’ just got away from work.”
    a propos this interesting comment, my husband not only lost weight after leaving the office for good, he also stopped snoring. has anyone studied this?

  26. rmgw – “my husband not only lost weight after leaving the office for good, he also stopped snoring”

    My understanding is that weight loss can reduce snoring. I’m not a medical person, though.

  27. Harriet Hall says:

    werdna points out that “it’s dead easy to mis-measure something.” Very true. But calorie count estimates don’t need to be accurate. If you aim for 1500 calories and are not losing, you can cut down to 1400 and progressively lower as needed. Even if you are still underestimating how much you eat, you will eventually arrive at a weight-losing level despite any errors.

  28. Mark P says:

    that is, two quarter-pound hamburgers. One for lunch, one for dinner. For meat-eaters, that doesn’t sound extreme to me.

    And that’s the real concern for public health, right there.

    How can we fight obesity if people think two quarter-pound hamburgers per day is even remotely reasonable?

  29. Donna B. says:

    Is it the meat in the quarter pounder that’s so bad?

    I’m really not suggesting that anyone eat two of them a day or even two a week. That’s not the point.

    The point is that it is 8 oz. of ground beef in 2 quarter pounders which is about 500 calories. There are an additional 320 calories in the bun and condiments.

    If one ate 3 quarter pounders/day that is 1230 calories. So if quarter pounders as a meal are bad (as in the cause of obesity) it’s got to be something other than calories that is causing the weight gain.

    Now certainly someone who adds cheese, fries, and a soda to each meal is adding beaucoup calories and that could certainly be the cause of obesity.

    But that doesn’t mean it’s the meat or even the whole burger that’s the culprit.

  30. anoopbal says:

    “ut I am also struck in such studies, even intervention studies, by how small the difference are among the various diet types. This leads me to the conclusion that varying the ratios of macronutients (protein, carbohydrates, and fats) is of little ultimate utility in weight control. ”

    You are right indeed.

    The below was one of the studies which received a lot of accolades and it shows exactly what you just wrote.

    N Engl J Med. 2009 Feb 26;360(9):859-73.
    Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates.

    Sacks FM, Bray GA, Carey VJ, Smith SR, Ryan DH, Anton SD, McManus K, Champagne CM, Bishop LM, Laranjo N, Leboff MS, Rood JC, de Jonge L, Greenway FL, Loria CM, Obarzanek E, Williamson DA.

    Department of Nutrition, Harvard School of Public Health, Boston, USA..

    BACKGROUND: The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year. METHODS: We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content. RESULTS: At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels.

    CONCLUSIONS: Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize.

  31. Steve says:

    I am consistently shocked by how many people believe that they can create matter. They believe that they take in 1lb of any nutrient that they can somehow increase their body fat content greater than the weight of nutrients consumed. IE creating mass. People do not recognize fluid shifts and have confirmation bias resulting in a belief that they can gain 2lbs from a 10oz slice of cake. Discounting conservation of mass, and thermodynamics. This is all over dietary psuedoscience. Simple formula: calories in > calories burned= weight gain, Calories in < Calories burned= weight loss. Fluid affects measurement but not intrinsic fat storage. You can speed the process with tweaks in nutrients, activity and ways of tricking your satiety/metabolism. In the end we are ruled by simple laws of thermodynamics same as everything else.

  32. Bacteriophile says:

    Two thoughts:

    Is it possible that certain types of food lead to feelings of fullness but don’t have large amounts of calories? I suppose that’s calorie density, actually. Is it possible that plant foods are generally less calorie-dense than meats?

    Is it possible that adjusting macronutrient ratios in certain ways DOES have large effects for certain types of people, while adjusting in other ways has large effects for other types? It seems like such individual differences would be averaged out in such large sample sizes.

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