US Study: The accumulation of "marbled meat" in the thighs increases with the consumption of ultra-processed foods

Recently CNN.com.jp reported the following:

(Diet with 29.5% processed food at the left vs 87.1% at the right)

太ももに蓄積する「霜降り肉」、超加工食品の摂取が多いほど増加　米研究

2026.04.15 Wed posted at 11:00 JST

 （CNN） 見事な霜降りの入った高級肉のように見える画像は、きめ細かく柔らかなステーキを思わせる。しかしこれは、超加工食品が年間摂取カロリーの87％を占めていた62歳の女性の太ももをMRIで撮影した画像だった。

米カリフォルニア大学のゼーラ・アッカヤ氏によると、この女性の食事はシリアルやチョコレート菓子、キャンディ菓子、清涼飲料水や加糖飲料が中心だったという。

筋肉繊維の間や内側に隠れた脂肪は深刻な健康問題の兆候かもしれないと同氏は指摘する。アッカヤ氏のチームは、膝（ひざ）の骨粗しょう症リスクがある人の筋肉内脂肪に対して超加工食品が及ぼす影響について調査した。

超加工食品は、体重増加や肥満、がん、心血管疾患、2型糖尿病、うつ病といった慢性疾患との関係が指摘されており、寿命を縮める可能性さえある。

米疾病対策センター（CDC）によれば、米国の成人はカロリーの50％以上を超加工食品から摂取している。子どもの場合、その数字は62％に跳ね上がる。

今回の調査対象となった別の61歳の女性の場合、やはり太ももの筋肉に「霜降り」はあったものの、それほどの量ではなかった。この女性の年間の食事に占める超加工食品の割合は約29％だった。

「こうした人たちはMRI検査の時点で膝の変形性関節症の兆候はなかったにもかかわらず、既に筋肉の質の低下が見られたことは特に懸念が大きい」とアッカヤ氏は話す。

犯人は超加工食品？

今回の研究結果は14日の放射線医学誌に掲載された。研究チームは、膝変形性関節症の予防と治療を目的とする全米規模の調査プロジェクト「変形性関節症イニシアチブ」に参加した615人のMRI診断画像を分析。対象者の平均年齢は60歳、体格指数（BMI）は27で、膝の変形性関節症の兆候がある人はいなかった。

BMIは25～29.9が過体重、30～34.9が肥満、35～39.9は肥満度2、40以上は「重度の」肥満（肥満度3）と分類される。

食事の29.5％を超加工食品が占める61歳女性の場合、BMIは32.6だった。一方、超加工食品の割合が87.1％だった女性のBMIは31.8と、61歳女性に比べればやや低く、活動スコアも高かったにもかかわらず、太ももの「霜降り」の量ははるかに多かった。

「カロリー摂取量に関係なく、全般的に超加工食品の摂取量が多いほど、大腿（だいたい）筋の筋内脂肪が多かった」。論文筆頭著者のトーマス・リンク氏はそう解説する。

米ニューヨーク大学のミリアム・ブレデラ氏は今回の研究について、超加工食品が筋肉の霜降り化の原因になっていることを証明したわけではないとしながらも、「強い関係」が見られたと指摘。「ただ、どのくらい超加工食品を食べ続ければ筋肉がこうなるのかは分からない」とした。

その上で、「分かっているのは、筋肉内に蓄積した脂肪がある場合、運動と健康的な食生活を始めれば、間違いなく筋肉の質は改善できるということ」とブレデラ氏は話し、「年を取ってからよりも若い時の方がずっと簡単だが、やればできる」と言い添えた。

Translation

US Study: The accumulation of "marbled meat" in the thighs increases with the consumption of ultra-processed foods

(CNN) The image, which looks like a finely marbled, high-quality cut of meat, resembled a tender steak. However, this was an MRI scan of the thigh of a 62-year-old woman whose annual calorie intake consisted of 87% ultra-processed foods.

According to Zella Akkaya of the University of California, this woman's diet mainly consisted of cereals, chocolates, candies, soft drinks, and sugary beverages.

Akkaya pointed out that fat hidden between and inside muscle fibers might be a sign of serious health problems. Akkaya's team investigated the effects of ultra-processed foods on intramuscular fat in people at risk of knee osteoporosis.

Ultra-processed foods had been linked to weight gain, obesity, cancer, cardiovascular disease, type 2 diabetes, and depression, and might even shorten lifespan.

According to the U.S. Centers for Disease Control and Prevention (CDC), American adults obtained more than 50% of their calories from ultra-processed foods. For children, that figure jumps to 62%.

In the case of another 61-year-old woman included in this study, while she did have some "marbling" in her thigh muscles, it wasn't as pronounced. Ultra-processed foods accounted for approximately 29% of this woman's annual diet.

Akkaya said "The fact that these individuals showed no signs of osteoarthritis of the knee at the time of MRI scans, yet they already exhibited a decline in muscle quality and is particularly a big concern."

Ultra-processed foods as the culprit?

The findings of this study were published in the Journal of Radiology on the 14th. The research team analyzed MRI images of 615 participants in the "Osteoarthritis Initiative," a nationwide survey project aimed at preventing and treating knee osteoarthritis. The average age of the participants was 60, their body mass index (BMI) was 27, and none showed signs of knee osteoarthritis.

A BMI of 25-29.9 is classified as overweight, 30-34.9 as obese, 35-39.9 as obesity level 2, and 40 or higher as "severe" obesity (obesity level 3).

A 61-year-old woman whose diet consisted of 29.5% ultra-processed foods had a BMI of 32.6. In contrast, a woman whose diet consisted of 87.1% ultra-processed foods had a BMI of 31.8, which was slightly lower than the 61-year-old woman, yet she had significantly more "marbling" in her thighs, despite having a higher activity score.

Thomas Link, as the lead author of the paper explained that "Regardless of calorie intake, the higher the overall intake of ultra-processed foods, the more intramuscular fat in the thigh muscles."

Miriam Bredera of New York University noted that while the study didn't prove that ultra-processed foods directly cause muscle marbling, a "strong correlation" was observed. He said "However, I don't know how long you have to keep eating ultra-processed foods to get muscles like that."

On top of that, Bredera said “What I do know is that if you have fat stored in your muscles, you can definitely improve the quality of your muscles by starting exercise and a healthy diet," and added that " It's much easier when you're young than when you're older, but you can do it if you try. "

So, fat hidden between and inside muscle fibers may be a sign of serious health problems. Ultra-processed foods have been linked to weight gain, obesity, cancer, cardiovascular disease, type 2 diabetes, and depression, and may even shorten lifespan. Apparently, the plain fact is that regardless of calorie intake, the higher the overall intake of ultra-processed foods, the more intramuscular fat could be found in the thigh muscles.