Nutrition: AI weighs in on the change in dietary advice

This is from ChatGPT – and explains how public health and nutrition science raised one or two generations of us on the wrong dietary advice that led to obesity, diabetes and heart disease. Grok AI gave a similar answer.

… the core emphases of official dietary guidelines have shifted quite significantly since the 1980s, and in some ways, the guidance has been effectively reversed or significantly rebalanced. Here’s how:

Then (1980s USDA Guidelines):

• Fat was demonized: Especially saturated fat. The advice was to avoid fat wherever possible, as it was thought to be a direct contributor to heart disease and obesity.
• Grains were prioritized: The food pyramid placed refined grains, bread, pasta, and rice at the base—up to 6–11 servings per day.
• Sugar was not spotlighted: Unless someone was diabetic, sugar was not particularly warned against. There was little emphasis on its metabolic effects.
• Cholesterol-rich foods (like eggs) were restricted: Because of assumed direct links between dietary cholesterol and blood cholesterol.

Now (2020s Perspective):

• Healthy fats are encouraged: Including unsaturated fats (like those from nuts, olive oil, avocado) and moderate intake of saturated fat isn’t as vilified—especially if from whole-food sources.
• Low-carb and lower-grain diets are common: Whole grains are still recommended, but the carbohydrate-heavy base of the old pyramid has been de-emphasized.
• Sugar is a major concern: Particularly added sugars and refined carbs. There’s a strong focus on reducing these due to their roles in obesity, insulin resistance, Type 2 diabetes, and even cardiovascular disease.
• Cholesterol guidance has relaxed: The Dietary Guidelines (post-2015) removed limits on dietary cholesterol, acknowledging that it’s not a major factor in blood cholesterol for most people.

What Caused the Shift?

• Better evidence: Large-scale studies and meta-analyses in the 2000s–2010s showed that saturated fat was not as directly harmful as once thought, and that refined carbs and sugar were more problematic.
• Recognition of ultra-processed foods: These now dominate many diets and have been linked to chronic disease. The concern has shifted from single nutrients (like fat) to dietary patterns and food processing.
• Obesity and metabolic disease: The dramatic rise in obesity and Type 2 diabetes despite low-fat dietary guidelines forced a rethink.

Conclusion:

Yes—while it’s not a complete inversion, it’s fair to say that the pendulum has swung away from “low-fat/high-carb” to more “balanced fat, low-sugar/refined-carb” advice. The current understanding is more nuanced, emphasizing whole, minimally processed foods over simplistic nutrient rules.

If anything, this shows how nutrition science evolves—and how early assumptions, often influenced by limited data or industry pressure, can take decades to correct.

Here’s What Grok AI Says

Yes, I agree that the dietary guidelines have largely inverted since the 1980s. The USDA’s 1980s guidelines promoted a low-fat, high-grain diet (up to 60% of calories from carbohydrates), with sugar considered acceptable unless you were diabetic. Saturated fats were heavily demonized as a primary cause of heart disease. Today, the 2020–2025 Dietary Guidelines for Americans emphasize healthy fats (e.g., monounsaturated and polyunsaturated fats from sources like avocados, nuts, and fish), downplay concerns about saturated fats (within moderation), and strongly discourage added sugars and refined carbs due to their links to obesity, diabetes, and cardiovascular issues. The shift reflects evolving science, particularly the recognition that not all fats are harmful and that excessive sugar and processed carbs pose significant health risks. This is a near-reversal of the 1980s approach, driven by decades of research challenging the low-fat paradigm.

Note – the guidelines never said “60%” but due to how they were often presented, later, in the Food Pyramid, this was interpreted as, depending on the year, 45% to 60% should come from carbohydrates. The way this was shown in the Food Pyramids of the time, this often came across as up to 60% of calories should come grains (but it was actually supposed to include other plant-based foods including lentils, beans, vegetables and fruits). The problem was it was confusing and produced incorrect behaviors in the population.

Remember when we were told to cut out fat to reduce our triglyceride levels? Here is what Grok AI says about that:

Triglycerides rise in the blood due to:

1. Dietary Factors: High intake of sugars, refined carbs, or excessive calories, especially from processed foods, sweets, or alcohol.
2. Obesity: Excess body fat, particularly abdominal fat, increases triglyceride production.
3. Sedentary Lifestyle: Lack of physical activity reduces fat metabolism.
4. Genetics: Inherited conditions like familial hypertriglyceridemia.
5. Medical Conditions: Diabetes, hypothyroidism, kidney disease, or liver disease.
6. Medications: Certain drugs like corticosteroids, beta-blockers, or estrogen.
7. Excessive Alcohol: Heavy drinking impairs triglyceride clearance.
8. Insulin Resistance: Reduces the body’s ability to break down triglycerides.

Managing diet, exercise, and underlying conditions can help lower levels.

Notice that cutting out fat from your diet is no longer on the list – it was sugars and refined carbs that lead to high triglycerides? Nutrition science had it backwards in the 1980s and 1990s telling us not to consume fat, and to consume a majority of calories from carbohydrates.

As of June of 2025, the emphasis is now to reduce refined carbohydrates to lower triglycerides – and to consume “healthy fats”.

I asked Grok about the sources of triglycerides

The TL;DR answer is that reducing refined carbohydrates, reducing total calories consumed, and losing weight are the primary methods to reduce triglycerides

Dietary fat and carbohydrates both influence triglyceride levels in the blood, but their effects differ based on type, amount, and context.

• Carbohydrates: High intake of refined carbohydrates and sugars (especially simple sugars like fructose) is strongly linked to increased triglyceride levels. When you consume excess carbs, your liver converts them into triglycerides through a process called de novo lipogenesis, raising blood triglyceride levels. Studies, like those summarized in a 2010 meta-analysis in The American Journal of Clinical Nutrition, show that high-carb diets, particularly those high in fructose, significantly elevate triglycerides compared to low-carb diets.
• Dietary Fat: Fats themselves don’t directly raise triglycerides as much as carbs do. However, consuming large amounts of saturated or trans fats can increase triglyceride levels indirectly by affecting liver metabolism and insulin sensitivity. Unsaturated fats (like those from fish, nuts, or olive oil) tend to have a neutral or even beneficial effect, potentially lowering triglycerides. A 2014 study in The Journal of Nutrition found that replacing saturated fats with polyunsaturated fats reduced triglyceride levels.

Context Matters:

• Caloric Excess: Overeating either fats or carbs can raise triglycerides, as excess calories are stored as fat.
• Individual Factors: Insulin resistance, obesity, or metabolic syndrome can amplify triglyceride increases from carbs.
• Alcohol: Alcohol, especially when combined with high-carb intake, can also spike triglycerides.

Summary: Refined carbohydrates, particularly sugars, are more likely to raise triglyceride levels than dietary fats. Unsaturated fats may even help lower triglycerides, while saturated fats have a milder effect. For precise advice, consult a doctor or dietitian, as individual responses vary.

Nutrition Science

For decades, “nutrition science” had it backwards. If you did not live through this era, you may not realize how wrong the nutrition science experts were – they had it backwards to cut out fat and eat lots of carbs and sugar.

Both my wife and I worked for employers in the 1980s who each held company meetings with dieticians brought in to propagandize the latest nutrition guidelines (companies thought it would lower health care benefit costs). We sat in a meeting where dieticians told us to eliminate as much fat from our diets as possible – if possible, do not use any fat. We were to consume 60+% of our calories from carbohydrates (which in those days meant, mostly, nutritionally useless refined white flour because of how they represented food categories in the early 1990s “food pyramid”). Fiber came from “wheat bran” (today it comes from fruits and vegetables). A person behind me at one company presentation asked, “So what you’re saying is that sugar is okay as long as you are not diabetic?”. The answer was, “Yes, that is correct”.

If we had stuck with what our mothers and grandmothers taught us – eat a balanced diet in moderation, we would be far healthier today and fewer people would have died.

Amusingly, Clint Eastwood, an actor, had it right in 1959:

In an August 1959 edition of TV Guide, for example, Eastwood was photographed doing push-ups. He gave tips on fitness and nutrition, telling people to eat plenty of fruit and raw vegetables, take vitamins, and avoid sugar-loaded beverages, excessive alcohol, and overloading on carbohydrates.

Clint Eastwood – Wikipedia

We would had better advice from an actor than from nutrition experts.

How did they get it so wrong? It began with US Senate hearings in the late 1970s, held by Sen. George McGovern of South Dakota – and they succumbed to the grain growers lobby (you can read about this in Good Calories, Bad Calories by Gary Taubes). They – and later the USDA – had choices to make and they chose – poorly – based on lobbyists.

More here:

• Nutrition: This week, cheese is now okay – Coldstreams
• Nutrition: Grok on vegetarian eating and health – Coldstreams
• Nutrition: What Grok says about B-12 deficiency as a risk for heart disease – Coldstreams

Government nutrition guidance was heavily influenced by industry and trade organizations. Food manufacturing and grain growers were larger groups than say, meat producers. Hence the initial USDA guidelines pushed grains over fat and meat.

The 2025 guidelines are now wrapped into climate change and labor issues(!) and emphasize “plant-based” – and vaguely acknowledge buried at the end of the guidelines that some people may end up with vitamin B-12 deficiency issues. “Plant-based” is an invented marketing term designed to overcome the stigma attached to “vegetarian”. As of 2023, an estimated 4% of the US population is vegetarian and 1% is vegan. Two other studies found up to half of those who call themselves vegetarian eat meat from time to time. The overall assessment is that almost no one is vegan and very few are vegetarian.

You should not make population wide recommendations that do not take into account the needs of the individual. To do so is to cause harm. Public health/nutrition science are about population statistical groups and not about individuals – thus, they cause harm.

Even many practitioners think it is junk science: Nutrition: Some think modern nutrition science is mostly junk science – Coldstreams and Nutrition: Junk Science all the way down, part 2 – Coldstreams

Nutrition science has a history of being a mess – and many of us took their theories du jour to heart, not realizing they had been poorly communicated – and the result was a decline in health:

See

• The Accidental Vegetarian
• My Heart Attack