Hey there!

As an engineer, here's something that's been bugging me for a while: why (and when) did the US publish updated dietary guidelines—avoiding fats and pushing carbs—and do those dates correspond to increases in obesity and diabetes?

In my mind, they were linked.

So I asked my research assistant, Claude, to go pull the data and see if he could find a correlation. Note: correlation doesn't automatically mean causation.

Here's what Claude found:

The three pivot points

1956 — The "Basic Four." Harvard School of Public Health researchers condensed the USDA's wartime "Basic Seven" food groups down to four: milk, meat, fruits & vegetables, and bread & cereals. The USDA adopted it that year, and it stayed the official guide until 1992. At the time, obesity sat around 13% of American adults.

1977 — The McGovern Report. This is the real pivot. Senator George McGovern's Senate Select Committee on Nutrition and Human Needs released "Dietary Goals for the United States," recommending:

• Carbohydrates up to 55–60% of daily calories
• Total fat down from ~40% to 30% of calories
• Less saturated fat, cholesterol, sugar, and salt
• Less meat and eggs; whole milk swapped for nonfat

The science behind it came from four advisors — Dr. Mark Hegsted (Harvard), Dr. Philip Lee, Dr. Sheldon Margen, and Dr. Beverly Winikoff. Worth noting: Hegsted had accepted funding from the Sugar Association, and his Harvard department head had industry sugar funding too — a detail that's fueled ongoing debate about whether fat got unfairly targeted while sugar got a pass.

1980 — It becomes official. The USDA and HHS jointly issued the first "Dietary Guidelines for Americans," built directly on the McGovern Report's low-fat, high-carb framework. Reaffirmed in 1985 and 1990.

1992 — The pyramid. Bread, cereal, rice, and pasta became the largest base (6–11 servings/day). Fats, oils, and sweets got squeezed into the tiny tip, to be used "sparingly."

The obesity data (NHANES, measured — not self-reported)

• 1960–1962: ~13%
• 1971–1974: ~15%
• 1976–1980: ~15%
• 1988–1994: ~23%
• 1999–2000: ~31%
• 2009–2010: ~36%
• 2021–2023: ~40.3% (plus 31.7% overweight)

Severe obesity climbed even faster in relative terms — from under 1% in the early 1960s to nearly 10% today. Childhood obesity roughly tripled, from about 5% in the early 1970s to over 21% now.

The diabetes data tells the same story

Diagnosed diabetes prevalence went from 0.93% of the US population in 1958 to 6.95% in 2010 to 7.4% in 2015. CDC's latest figures put total diabetes — diagnosed plus undiagnosed — at roughly 12% of American adults today. That's more than a twelvefold increase since 1958, and the steepest sustained climb happened in exactly the decades following the shift to a low-fat, high-carbohydrate diet.

Connecting the dots

Carbohydrate consumption had actually been declining in the US from 1909 through 1963. Then it reversed — and the climb accelerated sharply right around 1980, the same year the low-fat, high-carb guidelines became official policy. Much of that increase traces back to corn syrup sweeteners: once fat became the villain, food manufacturers reformulated "low-fat" products by swapping in sugar and refined carbs instead.

The obesity and diabetes curves tell the same story. Rates held fairly steady through the 1970s, then began the steepest sustained climb in US history starting in the early 1980s — continuing upward through the 90s and 2000s, right alongside the dietary shift.

Correlation isn't causation, but the timing is hard to ignore: 1977 report → 1980 guidelines → fat demonized, carbs substituted in → obesity and diabetes acceleration.

The lesson underneath the data

As an engineer who worked to analyze and establish safe operating limits for critical rotating engine parts for over 20 years of my 35-year engineering career, I can tell you this would never have happened with an engineer in charge.

We are trained to get data and check assumptions.

Jet engine design is on the cutting edge of technology. We keep pushing for more efficient engines, which means pushing cycle temperatures up, which means pushing materials technology to handle the stresses and hold times at high temperatures.

Which also means evaluating failure mechanisms and designing for them. And being on the lookout for new failure mechanisms and establishing new tests to evaluate the life impact.

We have an established methodology for establishing safe operating limits that addresses how the engine model is flown, detailed heat transfer and stress analysis of critical features on each engine component, which — when combined with materials test data — enables us to calculate statistically significant minimum calculated lives, to which an additional safety factor is applied.

We also have established inspection procedures, some completed on wing, others completed at service overhauls. The bottom line is we don't institute major design changes without monitoring field performance. If something starts drifting from our predictions, we do a root-cause analysis and launch redesign and/or repair efforts.

The bottom line: engineers are trained to check data and assumptions.

When we initiate major design changes, we mitigate the risk with demonstrator engines to gain experience.

The commercial aviation business has been called a "Sporty Game" by John Newhouse. There's a lot at risk with new technology development. As engineers, we manage the risk as best we can through strategic planning and testing.

In contrast, the US issued a change in dietary guidelines based on the interpretation of four advisors, no controlled studies of sufficient length to determine adverse impact, plus some of the work was funded by a sugar company.

What Engineering Would Have Required

Engineers require a tested hypothesis before changing a design. Dietary policy got the interpretation of four advisors on contested science.

Engineers require a monitored baseline. Surveillance data existed (NHANES began in 1960) — but it was never formally tied back into the guidelines.

Engineers require controlled testing before wide deployment. No controlled trial preceded a nationwide dietary shift. It went straight to policy.

Engineers require continuous monitoring for failure signals. Obesity and diabetes data climbed for decades without triggering a formal review.

I think it's time for the US to review its dietary recommendations in view of the havoc the McGovern report has wreaked.

This time, perhaps they'll put an engineer in charge.

More next week,

Marsha & Mooney

P.S. Remember the failure of the OceanGate Titan submersible that imploded in 2023, killing five people, including CEO and pilot Stockton Rush, billionaire explorer Hamish Harding, and veteran Titanic diver Paul-Henri Nargeolet?
That's a classic example of what can happen when you do insufficient testing. The Coast Guard's investigation later found that Rush had skipped independent certification for the carbon-fiber hull, which was fundamentally unsuited to withstand repeated deep-sea pressure cycles — a material failure mode that proper testing would have caught before anyone stepped aboard. Different industry, same lesson: skip the rigor, and pay the consequences.

Sources

• Harvard T.H. Chan School of Public Health, "A visual history of food guides"
• Britannica, "Dietary Guidelines for Americans"
• CDC/NCHS, "Prevalence of Overweight, Obesity, and Severe Obesity Among Adults Age 20 and Older: United States, 1960–1962 Through August 2021–August 2023"
• CDC, "Long-term Trends in Diabetes" and "National Diabetes Statistics Report"
• US Coast Guard Marine Board of Investigation, Titan submersible implosion report (2025)

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