二つの肥満仮説
Two obesity hypotheses肥満に関して、二つの仮説がある。
- カロリー説。 摂取カロリーが消費カロリーを上回ると、超過分のカロリーが脂肪に置き換えるという仮説である。この場合、痩せるためには、消費カロリーを増やすか、摂取カロリーを減らすことが必要である。
- ホルモン説(炭水化物説)。 炭水化物摂取によってインスリンが放出されて脂肪細胞が刺激されて脂肪の燃焼が妨げられる。インスリン濃度が上昇した状態が続くと体重が増える。したがって、痩せるためには炭水化物摂取制限をし、インスリン濃度の上昇を防ぐことが必要である。
There are two hypotheses concerning obesity
トーベス(2013, 日経サイエンス、2013年12月号) によれば、ホルモン説が注目を浴びているが、検証には成功していない。摂取カロリーを統制して、炭水化物の効果を調べる必要があるが、炭水化物1g 4 kcal, タンパク質1g 4 kcal, 脂質1g 9kcalは食物の形態や消化率を無視した値で、かなり統制が難しい。この辺りの統制不能の誤差が研究結果に混入していると思う。
- Calorie theory. When an ingestion calorie exceeds a consumption calorie, an exceeded calorie transposes to fat. In this case, in order to become thin, it is required to increase a consumption calorie or to reduce an ingestion calorie.
- Hormone theory (carbohydrate theory). An insulin is emitted by carbohydrate ingestion, adipose cells are stimulated, and combustion of fat is barred. If the insulin concentration remains high level, body weight will increase. Therefore, it is required to carry out carbohydrate ingestion restrictions, in order to become thin, and to prevent the rise of insulin concentration.
トーベス(2013, 日経サイエンス、2013年12月号) によれば、ホルモン説が注目を浴びているが、検証には成功していない。摂取カロリーを統制して、炭水化物の効果を調べる必要があるが、炭水化物1g 4 kcal, タンパク質1g 4 kcal, 脂質1g 9kcalは食物の形態や消化率を無視した値で、かなり統制が難しい。この辺りの統制不能の誤差が研究結果に混入していると思う。
According Taubes(2013, Nikkei Science, the December, 2013 issue) , the hormone theory is capturing the spotlight, but its verification is not succeeded. Although it is necessary to control an ingestion calorie and to investigate the effect of carbohydrate. The calorie value of each gram of carbohydrate 4 kcal, protein 4 kcal, and lipid 9 kcal are the values which disregarded the form and digestive rate of food. Therefore the control of intake calorie is quite difficult. I think that this kind of error is mixed in research findings.
いくつか、メタ分析を行ったレビューを読んでみた。ジョンスンら(2013) は砂糖の取り過ぎが肥満、メタボリック症候群、糖尿病を引き起こすという。ネズミの実験では果糖がインスリン抵抗性(インスリンの分泌があっても血糖値が下がらないこと)や血圧を上げるという。また、体重の増加とは関係なしに、メタボリック症候群が発展するらしい。彼らは人間で行われたいくつかのランダム化比較研究をレビューしている。それによると、糖分を投与されたグループは体重が増え、インシュリン抵抗性が大きくなった。また、糖分を含んだ飲み物とミルクや水などの飲み物を与えた比較研究では、統制群に比較して脂肪組織や体重が増えた。
I have read several systematic reviews which conducted meta analysis. Johnson et al(2013) maintained the sugar caused overweight, metabolic syndrome, and diabetes. Fructose raises insulin resistance ( this means that if there is secretion of an insulin, the blood sugar level do not decrease) and blood pressure in rats. Moreover, seemingly, metabolic syndrome will develop without the relation to the increase in weight. They reviewed the randomized comparative studies in men. According to them, the intake of fructose increased body weight and insulin resistance level. Moreover, the subject receiving sugary soft drink gained more liver fat, cholesterol and weight as compared to the control group.
一方、カーンら(2014)のレビューでは砂糖を強調しすぎであるという。確かに、砂糖の摂取量は2000年からは減少しているが、肥満者は増え続けている。レビューによると、砂糖に関するランダム化比較試験では、砂糖を通常の食事に追加した場合に体重が増えるが、摂取カロリーが一定の場合は体重は変化しない。ジョンスンらは摂取カロリーが一定でも砂糖が血清中の尿酸値を上げることを示したが、肝臓の生理指標にはほとんど影響がなかった。エネルギー消費を摂取カロリーで統制すると、砂糖は体重には何の影響も与えない。
On the other hand, Kahn et al(2014) criticized that role of dietary sugar was emphasized too much. Surely, although the estimated intake of sugar is decreasing from 2000, the number of obesity persons are increasing. According to this review, when sugar was added to the usual meal, weight increased, but when intake calorie was constant, weight did not change in many randomized controlled trials. Johnson et al.(2013) showed that sugar increased the uric acid in serum, but it had no effect on a wide variety of hepatic biomarkers. Kahn et al. asserted that sugar gave no influence on body weight when energy consumption was controlled by intake calorie.
カーンらの砂糖の想定される効果をまとめた表を引用しておこう。砂糖を同一カロリーの他の食品への変更しても体重の増加は見られないし、糖尿病の原因になるというエビテンスもない。もちろん、摂取カロリーを増やすと太るし、砂糖は過剰なカロリーを提供してしまう。
I will cite a summary table of Kahn et al.(2014) on the putative effects of sugar. The body weight did not increase when sugar was changed to other isocaloric nutrients. And, there is no evidence that sugar caused diabetes. Of course, excessive intake calorie causes weight increase, and sugar provides unnecessary calorie.
On the other hand, Kahn et al(2014) criticized that role of dietary sugar was emphasized too much. Surely, although the estimated intake of sugar is decreasing from 2000, the number of obesity persons are increasing. According to this review, when sugar was added to the usual meal, weight increased, but when intake calorie was constant, weight did not change in many randomized controlled trials. Johnson et al.(2013) showed that sugar increased the uric acid in serum, but it had no effect on a wide variety of hepatic biomarkers. Kahn et al. asserted that sugar gave no influence on body weight when energy consumption was controlled by intake calorie.
カーンらの砂糖の想定される効果をまとめた表を引用しておこう。砂糖を同一カロリーの他の食品への変更しても体重の増加は見られないし、糖尿病の原因になるというエビテンスもない。もちろん、摂取カロリーを増やすと太るし、砂糖は過剰なカロリーを提供してしまう。
I will cite a summary table of Kahn et al.(2014) on the putative effects of sugar. The body weight did not increase when sugar was changed to other isocaloric nutrients. And, there is no evidence that sugar caused diabetes. Of course, excessive intake calorie causes weight increase, and sugar provides unnecessary calorie.
日経サイエンスの記事の執筆者は、ホルモン説に立ち、近い将来に実証されそうに書いているが、他の論文を読んでみると、この仮説を支持するエビデンスもなく、実証は簡単ではないようだ。
Taubes(2013, Nikkei Science, the December, 2013 issue) was standing on hormone theory, and he gave us an impression that this theory was proved in near future. But, I think it is not easy to prove this theory after reading several systematic reviews, because of the lack of evidence.肥満治療の長期効果
The long-term effect of intervention of obesity
I have read several systematic reviews which carried out the meta analysis of intervention studies of obesity. Especially, the long-term effect must be important. Johansson, et al. (2014) evaluated the long-term effects of ant-obesity drugs, meal supplement, high-protein diet, dietary supplements, other diet, or exercise on weight loss maintenance after initial very low calorie diet (below 800 kcal / day) and a low-calorie-content diet (1200 kcal or less / day) term for one or two months. Their meta analysis included 20 randomized control trials, the total number of subjects were 3017. The treatment periods were from half a year to three years.
統制群は灰色の直線、実験群は色の直線で描かれている。サプリメントは統制群との差がまったくなく、効果がない。高タンパク食は5カ月のフォローアップ期間で統制群との差が1.5kgと効果があった。また、マクロ栄養(低脂肪)は統制群との差が1.2kgで効果があった。運動は0.8kgの差しかなく、統計的に意味のある差ではなかった。肥満防止薬は20カ月後でも体重の増加がなく、統制群より3.5kg軽い。また、食事の代替物(おそらく超低カロリーの物)は18カ月後でリバウンドはあるが、統制群よりも3.9kg軽い。つまり、もっとも効果があったのは薬物や食事の代替物であった。
The results of control group were drawn in gray straight lines, and that of experimental group were drawn in color straight lines. Dietary supplement had no effect compared to the control group. High-protein diet had significant difference in the five months follow-up period. The discrepancy was 1.5 kg. And macronutrition ( low fat ) had significant difference with a control group. Its discrepancy was 1.2 kg. Exercise had no significant difference, which was only a 0.8 kg difference. Also after 20 months, anti-obesity drugs had significant prevention effects. The weight of anti-obesity group was lighter than a control group 3.5 kg. Moreover, meal replacement (it may be super-low calorie food) group was lighter than a control group 3.9 kg, although there was a little rebound in 18 months. In sum, anti-obesity drug and meal replacement were the most effective.
The results of control group were drawn in gray straight lines, and that of experimental group were drawn in color straight lines. Dietary supplement had no effect compared to the control group. High-protein diet had significant difference in the five months follow-up period. The discrepancy was 1.5 kg. And macronutrition ( low fat ) had significant difference with a control group. Its discrepancy was 1.2 kg. Exercise had no significant difference, which was only a 0.8 kg difference. Also after 20 months, anti-obesity drugs had significant prevention effects. The weight of anti-obesity group was lighter than a control group 3.5 kg. Moreover, meal replacement (it may be super-low calorie food) group was lighter than a control group 3.9 kg, although there was a little rebound in 18 months. In sum, anti-obesity drug and meal replacement were the most effective.
一方、シュイングハックルら(2013) は、データベースから高タンパクダイエットに関するランダム化比較研究15を選び、心臓循環系、メタボの危険要因を検討した。研究期間は12カ月から24カ月であった。高タンパクダイエットは空腹時血糖値を除き、体重や腰回りなど、すべての危険因子に関して有意水準に達しなかった。肥満に対して、高タンパクダイエットを推奨するには時期尚早であるという。
On the other hand, Schwinghackl et al.(2013) chose the 15 randomized comparative studies about a high-protein diet from the database, and examined cardiovascular and metabolic risk factors. The intervention terms were from 12 to 24 months. The high-protein diet did not reached the significance level about the risk factors, such as weight and waist, except for the fasting blood sugar level. They asserted that it was premature for recommending high-protein diet to obesity.
On the other hand, Schwinghackl et al.(2013) chose the 15 randomized comparative studies about a high-protein diet from the database, and examined cardiovascular and metabolic risk factors. The intervention terms were from 12 to 24 months. The high-protein diet did not reached the significance level about the risk factors, such as weight and waist, except for the fasting blood sugar level. They asserted that it was premature for recommending high-protein diet to obesity.
暫定的結論
Provisional conclusion
日経サイエンスの記事はホルモン説を支持する著者によって書かれたので、ホルモン説が正しそうな印象を受ける。しかし、メタ分析を行った系統的レビューをいくつか読むと、カロリー説のエビデンスはある程度あり、ホルモン説のエビデンスが乏しいという印象を受けた。また、肥満への介入研究を見ると、体重を減らした後の維持はかなり難しく、運動などでは効果がない。薬物は効果があるが、副作用がある。炭水化物制限を行いつつ、肉を無制限に食べるダイエットは、カロリー説のエビテンスと矛盾するので機能するはずがない。高タンパクダイエットは長期的には効果がないばかりか、窒素酸化物が増えるので、腎臓や肝臓等に負担がかかり、腎臓結石や痛風の危険が増える欠点もある。結局、体重を減らし、維持するには、特定の栄養素に偏ったダイエットをするのではなく、摂取カロリーを全体的に減らすしか方法はないだろう。
The article of Nikkei Science(2013, Nikkei Science, the December, 2013 issue) gave us an impression that the hormone theory seemed to be right, because the author was standing on hormone theory. However, when I read several systematic reviews which conducted meta analysis, I had an impression that there was much evidence of calorie theory, and the evidence of hormone theory was scarce. Moreover, the intervention studies of obesity tells us that the maintenance after reducing weight is quite difficult. That is, anti-obesity drug had significant effect but I am afraid that it may have much side effect. Regrettably, the exercise had no effect.
The diet permitted to eat meat without restriction while performing carbohydrate restrictions, had clear contradiction to calorie theory. This diet do not work well clearly. High-protein diet had no long-term effect to maintain the reduced weight, and it also burdens on the kidney, live etc, because much nitrogen oxide will be produced. There is also a risk factor of kidney stones or gout. After all, It is not recommended to rely on a specific nutrient diet. The only method to maintain our body weight may be the way to reduce intake calorie as a whole.
The article of Nikkei Science(2013, Nikkei Science, the December, 2013 issue) gave us an impression that the hormone theory seemed to be right, because the author was standing on hormone theory. However, when I read several systematic reviews which conducted meta analysis, I had an impression that there was much evidence of calorie theory, and the evidence of hormone theory was scarce. Moreover, the intervention studies of obesity tells us that the maintenance after reducing weight is quite difficult. That is, anti-obesity drug had significant effect but I am afraid that it may have much side effect. Regrettably, the exercise had no effect.
The diet permitted to eat meat without restriction while performing carbohydrate restrictions, had clear contradiction to calorie theory. This diet do not work well clearly. High-protein diet had no long-term effect to maintain the reduced weight, and it also burdens on the kidney, live etc, because much nitrogen oxide will be produced. There is also a risk factor of kidney stones or gout. After all, It is not recommended to rely on a specific nutrient diet. The only method to maintain our body weight may be the way to reduce intake calorie as a whole.
