The best thing to tell them is that the diets were neither low-carb nor Paleo.
The macronutrient breakdown was roughly 40% fat, 14% protein, and 46% carbohydrate.
From the full text:
Changing intake patterns for fat and carbohydrate 1986 to 2010
In 1986, mean reported fat intake, adjusted for age and BMI, was 39.2% of the men’s total reported energy intake (E%). Carbohydrates made up 45.9 E% and protein 13.6 E%. For women the corresponding levels were 35.5 E%, 49.2 E% and 14.3 E% for fat, carbohydrates and protein, respectively, in the same year (Figrue 2). From 1986 to 2010 two significant trend breaks in reported fat intake were identified for both men and women. A decrease from 1986 to 1992 resulted in a reduction of reported fat intake by 2.9 E% in men and 4.4 E% in women. These levels stayed largely stable until 2002–2004, and thereafter a significant increase occurred, and reported fat intake reached levels above those in 1986. Thus, in 2010 men got 39.9% and women 37.7% of their reported total energy intake from fat. The trends were similar in 10-year age groups (Additional file 1: Figure S1). Intake of saturated fat correlated highly with total fat, i.e. Spearman correlation coefficients were 0.86 for men and 0.87 for women. Reported intake of saturated fat followed a similar pattern as total fat, and the correlation coefficients were virtually identical each year (data not shown). In the same period reciprocal trend shifts were seen for reported carbohydrate intake (Figure 2). The fraction of energy originating from protein was virtually unchanged over the 25-year period, i.e. a slight increase by 0.9 E% was seen for both men and women but no significant trend break was identified (Figure 2).
Also, the foods associated with fat consumption were:
Time trends for foods associated with high fat intake Fats used for spreading on bread and cooking, dairy products, oil for salad dressing or cooking, various types of meats and sausages as main dish or on sandwiches, pizza, deep- fried potato chips (French fries), and non-sweet snacks (including potato and maize crisps (chips), cheese-flavoured puffed products, popcorn, and peanuts) were identified to be associated with high fat intake (fatE%)
Here's a link to the provisional PDF: http://www.nutritionj.com/content/pdf/1475-2891-11-40.pdf